A ship is a large watercraft
that travels the world's oceans and other sufficiently deep waterways
, carrying goods or passengers, or in support of specialized missions, such as defense, research, and fishing. Ships are generally distinguished from boat
s, based on size, shape, load capacity, and tradition. In the Age of Sail
" was a sailing vessel
defined by its sail plan of at least three square rig
and a full bowsprit
Ships have supported exploration
, and science
. After the 15th century, new crops
that had come from and to the Americas via the European seafarers significantly contributed to the world population growth
is responsible for the largest portion of world commerce.
As of 2016, there were more than 49,000 merchant ship
s, totaling almost 1.8 billion dead weight tons
. Of these 28% were oil tanker
s, 43% were bulk carrier
s, and 13% were container ship
Ships are generally larger than boats, but there is no universally accepted distinction between the two. Ships generally can remain at sea for longer periods of time than boats. A legal definition of ship from India
n case law
is a vessel that carries goods by sea.
A common notion is that a ship can carry a boat, but not ''vice versa''.
A US Navy rule of thumb is that ships heel towards the ''outside'' of a sharp turn, whereas boats heel towards the ''inside''
because of the relative location of the center of mass
versus the center of buoyancy
American and British 19th century maritime law distinguished "vessels" from other craft; ships and boats fall in one legal category, whereas open boats and rafts are not considered vessels.
In the Age of Sail
, a full-rigged ship
was a sailing vessel with at least three square-rigged masts and a full bowsprit
; other types of vessel
were also defined by their sailplan
, e.g. barque
A number of large vessels are usually referred to as boats. Submarine
s are a prime example. Other types of large vessel which are traditionally called boats are Great Lakes freighters
s, and ferryboat
Though large enough to carry their own boats and heavy cargoes, these vessels are designed for operation on inland or protected coastal waters.
In most maritime traditions ships have individual names
, and modern ships may belong to a ship class
often named after its first ship.
In the northern parts of Europe and America a ship is traditionally referred to with a female grammatical gender
, represented in English with the pronoun
"she", even if named after a man. This is not universal usage and some English language journalistic style guides
advise using "it" as referring to ships with female pronouns can be seen as offensive and outdated. In many documents the ship name is introduced with a ship prefix
being an abbreviation of the ship class, for example "MS" (motor ship) or "SV" (sailing vessel), making it easier to distinguish a ship name from other individual names in a text.
Prehistory and antiquity
The first sea-going sailing ships were developed by the Austronesian peoples
from what is now Taiwan
. Their invention of catamaran
, and crab claw sail
s enabled their ships to sail for vast distances in open ocean. It led to the Austronesian Expansion
at around 3000 to 1500 BC. From Taiwan, they rapidly colonized the islands of Maritime Southeast Asia
, then sailed further onwards to Micronesia
, Island Melanesia
, and Madagascar
, eventually colonizing a territory spanning half the globe.
Austronesian rigs were distinctive in that they had spars supporting both the upper and lower edges of the sails (and sometimes in between), in contrast to western rigs which only had a spar on the upper edge.
The sails were also made from woven leaves, usually from pandan
These were complemented by paddlers, who usually positioned themselves on platforms on the outrigger
s in the larger boats.
Austronesian ships ranged in complexity from simple dugout canoe
s with outriggers or lashed together to large edge-pegged plank-built boats built around a keel made from a dugout canoe. Their designs were unique, evolving from ancient rafts to the characteristic double-hulled, single-outrigger, and double-outrigger designs of Austronesian ships.
Early Austronesian sailors influenced the development of sailing technologies in Sri Lanka
and Southern India
through the Austronesian maritime trade network
of the Indian Ocean
, the precursor to the spice trade
route and the maritime silk road
, which was established at around 1500 BC.
Some scholars believe that the triangular Austronesian crab claw sail may have influenced the development of the lateen
sail in western ships due to early contact.
The junk rig
s of Chinese ships is also believed to be originally Javanese
In the 1st century AD, the people from Nusantara
archipelago already made large ships over 50 m long and stood out 4–7 m out of the water. They could carry 700-1000 people and 260 ton cargo. These ships known as ''kunlun bo'' or ''k'unlun po'' (崑崙舶, lit. "ship of the Kunlun
people") by the Chinese and ''kolandiaphonta'' by the Greeks. It has 4-7 masts and able to sail against the wind due to the usage of tanja sail
s. These ships reaching as far as Ghana
In China, miniature models of ships that feature steering oars have been dated to the Warring States period
(c. 475–221 BC).
By the Han dynasty
, a well kept naval fleet was an integral part of the military. Sternpost-mounted rudders started to appear on Chinese ship models starting in the 1st century AD.
However, these early Chinese ships were fluvial (riverine), and were not seaworthy.
The Chinese only acquired sea-going ship technologies in the 10th century AD Song Dynasty
after contact with Southeast Asian djong
trading ships, leading to the development of the junks
In 3000 BC, Ancient Egypt
ians learned how to assemble wooden planks
into a hull
They used woven strap
s to lash the planks together,
stuffed between the planks helped to seal the seams.
The Greek historian
and geographer Agatharchides
had documented ship-faring among the early Egyptians
: ''"During the prosperous period of the Old Kingdom
, between the 30th
and 25th centuries BC
, the river
-routes were kept in order, and Egyptian
ships sailed the Red Sea
as far as the myrrh
's ancient cedar wood ship Praise of the Two Lands
is the first reference recorded (2613 BC) to a ship being referred to by name.
The ancient Egypt
ians were perfectly at ease building sailboats. A remarkable example of their shipbuilding
skills was the Khufu ship
, a vessel in length entombed at the foot of the Great Pyramid of Giza
around 2500 BC and found intact in 1954.
The oldest discovered sea faring hulled boat is the Late Bronze Age Uluburun
shipwreck off the coast of Turkey, dating back to 1300 BC.
By 1200 B.C., the Phoenicia
ns were building large merchant ships. In world maritime history, declares Richard Woodman, they are recognized as "the first true seafarers, founding the art of pilotage, cabotage, and navigation" and the architects of "the first true ship, built of planks, capable of carrying a deadweight cargo and being sailed and steered."
14th through the 18th centuries
At this time, ships were developing in Asia in much the same way as Europe. Japan used defensive naval techniques in the Mongol invasions of Japan
in 1281. It is likely that the Mongols of the time took advantage of both European and Asian shipbuilding techniques. During the 15th century, China's Ming dynasty
assembled one of the largest and most powerful naval fleets in the world for the diplomatic and power projection voyages
of Zheng He
. Elsewhere in Japan in the 15th century, one of the world's first iron-clads, "Tekkōsen" (鉄甲船
), literally meaning "iron ships", was also developed. In Japan, during the Sengoku era
from the fifteenth to 17th century, the great struggle for feudal supremacy was fought, in part, by coastal fleets of several hundred boats, including the atakebune
. In Korea, in the early 15th century during the Joseon
"(거북선), was developed. The "turtle ship", as it was called is recognized as the first armored ship in the world.
Until the Renaissance
, navigational technology remained comparatively primitive compared to Austronesian cultures. This absence of technology did not prevent some civilizations from becoming sea powers. Examples include the maritime republics of Genoa
, Hanseatic League
, and the Byzantine navy
. The Viking
s used their knarr
s to explore North America
, trade in the Baltic Sea
and plunder many of the coastal regions of Western Europe.
Towards the end of the 14th century, ships like the carrack
began to develop towers on the bow and stern. These towers decreased the vessel's stability, and in the 15th century, the caravel
, designed by the Portuguese
, based on the Arabic ''qarib'' which could sail closer to the wind, became more widely used. The towers were gradually replaced by the forecastle
castle, as in the carrack ''Santa María''
of Christopher Columbus
. This increased freeboard
allowed another innovation: the freeing port
, and the artillery associated with it.
and then the caravel
were developed in Portugal
. After Columbus, European exploration
rapidly accelerated, and many new trade routes were established. In 1498, by reaching India, Vasco da Gama
proved that the access to the Indian Ocean
from the Atlantic
was possible. These explorations in the Atlantic and Indian Oceans were soon followed by France
and the Netherlands
, who explored the Portuguese and Spanish trade routes into the Pacific Ocean
, reaching Australia
in 1606 and New Zealand
Specialization and modernization
full-rigged ship ''Amerigo Vespucci''
in New York Harbor
Parallel to the development of warships, ships in service of marine fishery and trade also developed in the period between antiquity and the Renaissance.
Maritime trade was driven by the development of shipping companies with significant financial resources. Canal barges, towed by draft animals on an adjacent towpath
, contended with the railway
up to and past the early days of the industrial revolution
. Flat-bottomed and flexible scow
boats also became widely used for transporting small cargoes. Mercantile trade went hand-in-hand with exploration, self-financed by the commercial benefits of exploration.
During the first half of the 18th century, the French Navy
began to develop a new type of vessel known as a ship of the line
, featuring seventy-four guns. This type of ship became the backbone of all European fighting fleets. These ships were long and their construction required 2,800 oak trees and of rope; they carried a crew of about 800 sailors and soldiers.
During the 19th century the Royal Navy
enforced a ban on the slave trade
, acted to suppress piracy
, and continued to map the world. A clipper
was a very fast sailing ship of the 19th century. The clipper route
s fell into commercial disuse with the introduction of steam ships
with better fuel efficiency, and the opening of the Suez
and Panama Canal
Ship designs stayed fairly unchanged until the late 19th century. The industrial revolution, new mechanical methods of propulsion
, and the ability to construct ships from metal triggered an explosion in ship design. Factors including the quest for more efficient ships, the end of long running and wasteful maritime conflicts, and the increased financial capacity of industrial powers created an avalanche of more specialized boats and ships. Ships built for entirely new functions, such as firefighting, rescue, and research, also began to appear.
In 2019, the world's fleet included 51,684 commercial vessels with gross tonnage
of more than 1,000 tons
, totaling 1.96 billion tons. Such ships carried 11 billion tons of cargo in 2018, a sum that grew by 2.7% over the previous year. In terms of tonnage, 29% of ships were tankers
, 43% are bulk carrier
s, 13% container ship
s and 15% were other types.
In 2002, there were 1,240 warship
s operating in the world, not counting small vessels such as patrol boat
s. The United States
accounted for 3 million tons worth of these vessels, Russia
1.35 million tons, the United Kingdom
504,660 tons and China
402,830 tons. The 20th century saw many naval engagements during the two world war
s, the Cold War
, and the rise to power of naval forces of the two blocs. The world's major powers have recently used their naval power in cases such as the United Kingdom
in the Falkland Islands
and the United States
The size of the world's fishing fleet
is more difficult to estimate. The largest of these are counted as commercial vessels, but the smallest are legion. Fishing vessel
s can be found in most seaside villages in the world. As of 2004, the United Nations Food and Agriculture Organization
estimated 4 million fishing vessels were operating worldwide.
The same study estimated that the world's 29 million fishermen caught of fish and shellfish that year.
Types of ships
Because ships are constructed using the principles of naval architecture that require same structural components, their classification is based on their function such as that suggested by Paulet and Presles, which requires modification of the components. The categories accepted in general by naval architects are:
* High-speed craft
s including wave piercers, small-waterplane-area twin hull
(SWATH), surface effect ship
s and hovercraft
, wing in ground effect
* Off shore oil
vessels – Platform supply vessel
, pipe layers, accommodation and crane barge
s, non and semi-submersible drilling rig
s, production platforms
, floating production storage and offloading
* Fishing vessel
: Motorised fishing trawler
s, trap setters
& factory ship
: Traditional sailing
fishing vessels and boat
s used for handline fishing
, Pilot boat
:Floating dry docks
, floating cranes
* Dry cargo ships – tramp freighters, bulk carriers, cargo liners, container vessels, barge carriers, Ro-Ro ships, refrigerated cargo ships, timber carriers, livestock & light vehicle carriers.
* Liquid cargo ships – Oil tankers, liquefied gas carriers, chemical carriers.
* Passenger vessels
: Liners, cruise and Special Trade Passenger (STP) ships
: Cross-channel, coastal and harbour ferries.
: Luxury & cruising yachts
: Sail training and multi-masted ships
* Recreational boats and craft – rowed, masted and motorised craft
* Special-purpose vessels – weather
and research vessel
s, deep sea survey vessel
s, and icebreaker
* Submersibles – industrial exploration, scientific research, tourist and hydrographic survey.
and other surface combatants
– aircraft carrier
Some of these are discussed in the following sections.
thumb|''Hurma'', ''Hans'' and ''Voima'' at the _in_the_harbour_of_[[Imatra">Lake_Saimaa
_in_the_harbour_of_[[Imatra,_[[Finland.html" style="text-decoration: none;"class="mw-redirect" title="Imatra.html" style="text-decoration: none;"class="mw-redirect" title="Lake Saimaa in the harbour of [[Imatra">Lake Saimaa in the harbour of [[Imatra, [[Finland">Imatra.html" style="text-decoration: none;"class="mw-redirect" title="Lake Saimaa in the harbour of [[Imatra">Lake Saimaa in the harbour of [[Imatra, [[Finland, at a heritage ship meeting in 2009]]
Freshwater shipping may occur on lakes, rivers and canals. Ships designed for those venues may be specially adapted to the widths and depths of specific waterways. Examples of freshwater waterways that are navigable in part by large vessels include the Danube
Rivers, and the Great Lakes
s, also called lakers, are cargo
vessels that ply the Great Lakes
. The most well-known is , the latest major vessel to be wrecked on the Lakes. These vessels are traditionally called boats, not ships. Visiting ocean-going vessels are called "salties." Because of their additional beam
, very large salties are never seen inland of the Saint Lawrence Seaway
. Because the smallest of the Soo Locks
is larger than any Seaway lock, salties that can pass through the Seaway may travel anywhere in the Great Lakes. Because of their deeper draft, salties may accept partial loads on the Great Lakes, "topping off" when they have exited the Seaway. Similarly, the largest lakers are confined to the Upper Lakes (Superior
) because they are too large to use the Seaway locks, beginning at the Welland Canal
that bypasses the Niagara River
Since the freshwater
lakes are less corrosive to ships than the salt water
of the oceans, lakers tend to last much longer than ocean freighters. Lakers older than 50 years are not unusual, and as of 2005, all were over 20 years of age.
, built in 1906 as ''William P Snyder'', was the oldest laker still working on the Lakes until its conversion into a barge starting in 2013. Similarly, ''E.M. Ford'', built in 1898 as ''Presque Isle'', was sailing the lakes 98 years later in 1996. As of 2007 ''E.M. Ford'' was still afloat as a stationary transfer vessel at a riverside cement silo in Saginaw, Michigan
s are ships used for commercial purposes and can be divided into four broad categories: fishing, cargo ship
s, passenger ship
s, and special-purpose ships. The UNCTAD review of maritime transport
categorizes ships as: oil tankers, bulk (and combination) carriers, general cargo ships, container ships, and "other ships", which includes "liquefied petroleum gas carriers, liquefied natural gas carriers, parcel (chemical) tankers, specialized tankers, reefers, offshore supply, tugs, dredgers, cruise, ferries, other non-cargo". General cargo ships include "multi-purpose and project vessels and roll-on/roll-off cargo".
Modern commercial vessels are typically powered by a single propeller driven by a diesel
or, less usually, gas turbine engine
., but until the mid-19th century they were predominantly square sail rigged. The fastest vessels may use pump-jet engine
s. Most commercial vessels have full hull-forms to maximize cargo capacity. Hulls are usually made of steel, although aluminum can be used on faster craft, and fiberglass on the smallest service vessels. Commercial vessels generally have a crew headed by a sea captain
, with deck officer
s and engine officer
s on larger vessels. Special-purpose vessels often have specialized crew if necessary, for example scientists aboard research vessel
Fishing boats are generally small, often little more than but up to for a large tuna or whaling ship
. Aboard a fish processing vessel
, the catch can be made ready for market and sold more quickly once the ship makes port. Special purpose vessels have special gear. For example, trawlers have winches and arms, stern-trawlers have a rear ramp, and tuna seiners have skiffs. In 2004, of fish were caught in the marine capture fishery.
[UNFAO, 2007, p. 11.] Anchoveta
represented the largest single catch at .
That year, the top ten marine capture species also included Alaska pollock
, Blue whiting
, Skipjack tuna
, Atlantic herring
, Chub mackerel
, Japanese anchovy
, Chilean jack mackerel
, Largehead hairtail
, and Yellowfin tuna
Other species including salmon
, are also commercially fished. Modern commercial fishermen use many methods. One is fishing by nets
, such as purse seine
, beach seine, lift nets, gillnet
s, or entangling nets. Another is trawl
ing, including bottom trawl
and lines are used in methods like long-line fishing
and hand-line fishing
. Another method is the use of fishing trap
Cargo ships transport dry and liquid cargo. Dry cargo can be transported in bulk by bulk carrier
s, packed directly onto a general cargo ship
in break-bulk, packed in intermodal container
s as aboard a container ship
, or driven aboard as in roll-on roll-off ship
s. Liquid cargo is generally carried in bulk aboard tankers, such as oil tanker
s which may include both crude and finished products of oil, chemical tanker
s which may also carry vegetable oils other than chemicals and gas carrier
s, although smaller shipments may be carried on container ships in tank container
s range in size from small river ferries to very large cruise ship
s. This type of vessel includes ferries
, which move passengers and vehicles on short trips; ocean liner
s, which carry passengers from one place to another; and cruise ship
s, which carry passengers on voyages undertaken for pleasure, visiting several places and with leisure activities on board, often returning them to the port of embarkation. Riverboat
s and inland ferries
are specially designed to carry passengers, cargo, or both in the challenging river environment. Rivers present special hazards to vessels. They usually have varying water flows that alternately lead to high speed water flows or protruding rock hazards. Changing siltation patterns may cause the sudden appearance of shoal waters, and often floating or sunken logs and trees (called snags) can endanger the hulls and propulsion of riverboats. Riverboats are generally of shallow draft, being broad of beam and rather square in plan, with a low freeboard and high topsides. Riverboats can survive with this type of configuration as they do not have to withstand the high winds or large waves that are seen on large lakes, seas, or oceans.
s are a subset of commercial vessels, but generally small in size and often subject to different regulations and classification. They can be categorized by several criteria: architecture, the type of fish they catch, the fishing method used, geographical origin, and technical features such as rigging. As of 2004, the world's fishing fleet consisted of some 4 million vessels.
[UNFAO, 2007, p. 25.]
Of these, 1.3 million were decked vessels with enclosed areas and the rest were open vessels.
Most decked vessels were mechanized, but two-thirds of the open vessels were traditional craft propelled by sails and oars.
More than 60% of all existing large fishing vessels were built in Japan, Peru, the Russian Federation, Spain or the United States of America.
Special purpose vessels
A weather ship
was a ship stationed in the ocean
as a platform for surface and upper air meteorological observations for use in marine weather forecasting
. Surface weather observations were taken hourly, and four radiosonde releases occurred daily.
It was also meant to aid in search and rescue operations and to support transatlantic flights.
Proposed as early as 1927 by the aviation
community, the establishment of weather ships proved to be so useful during World War II
that the International Civil Aviation Organization
(ICAO) established a global network of weather ships in 1948, with 13 to be supplied by the United States.
This number was eventually negotiated down to nine.
The weather ship crews were normally at sea for three weeks at a time, returning to port for 10-day stretches.
Weather ship observations proved to be helpful in wind and wave studies, as they did not avoid weather systems like other ships tended to for safety reasons.
They were also helpful in monitoring storms at sea, such as tropical cyclone
s. The removal of a weather ship became a negative factor in forecasts leading up to the Great Storm of 1987
. Beginning in the 1970s, their role became largely superseded by weather buoy
s due to the ships' significant cost.
The agreement of the use of weather ships by the international community ended in 1990. The last weather ship was ''Polarfront
'', known as weather station M ("Mike"), which was put out of operation on 1 January 2010. Weather observations from ships continue from a fleet of voluntary merchant vessels
in routine commercial operation.
Naval vessels are those used by a navy
There have been many types of naval vessel
. Modern naval vessels can be broken down into three categories: surface warships
, and auxiliary ship
Modern warships are generally divided into seven main categories: aircraft carrier
s and amphibious assault ship
s. The distinction between cruisers, destroyers, frigates, and corvettes is not rigorous; the same vessel may be described differently in different navies. Battleship
s were used during the Second World War
and occasionally since then (the last battleships were removed from the U.S. Naval Vessel Register
in March 2006), but were made obsolete by the use of carrier-borne aircraft
and guided missile
Most military submarines are either attack submarine
s or ballistic missile submarine
s. Until the end of World War II
the primary role of the diesel/electric submarine was anti-ship warfare, inserting and removing covert agents and military forces, and intelligence-gathering. With the development of the homing torpedo
, better sonar
systems, and nuclear propulsion
, submarines also became able to effectively hunt each other. The development of submarine-launched nuclear
and cruise missiles
gave submarines a substantial and long-ranged ability to attack both land and sea targets with a variety of weapons ranging from cluster munition
s to nuclear weapon
also include many types of support and auxiliary vessel, such as minesweepers
, patrol boat
s, offshore patrol vessels
, replenishment ship
s, and hospital ship
s which are designated medical treatment
Fast combat vessels such as cruisers and destroyers usually have fine hulls to maximize speed and maneuverability. They also usually have advanced marine electronics
and communication systems, as well as weapons.
Some components exist in vessels of any size and purpose. Every vessel has a hull of sorts. Every vessel has some sort of propulsion, whether it's a pole, an ox, or a nuclear reactor. Most vessels have some sort of steering system. Other characteristics are common, but not as universal, such as compartments, holds, a superstructure, and equipment such as anchors and winches.
For a ship to float, its weight must be less than that of the water displaced by the ship's hull. There are many types of hulls, from logs lashed together to form a raft to the advanced hulls of America's Cup
sailboats. A vessel may have a single hull (called a monohull design), two in the case of catamaran
s, or three in the case of trimaran
s. Vessels with more than three hulls are rare, but some experiments have been conducted with designs such as pentamarans. Multiple hulls are generally parallel to each other and connected by rigid arms.
Hulls have several elements. The bow
is the foremost part of the hull. Many ships feature a bulbous bow
. The keel
is at the very bottom of the hull, extending the entire length of the ship. The rear part of the hull is known as the stern
, and many hulls have a flat back known as a transom
. Common hull appendages include propeller
s for propulsion, rudder
s for steering, and stabilizers
to quell a ship's rolling motion. Other hull features can be related to the vessel's work, such as fishing gear and sonar domes
Hulls are subject to various hydrostatic and hydrodynamic constraints. The key hydrostatic constraint is that it must be able to support the entire weight of the boat, and maintain stability even with often unevenly distributed weight. Hydrodynamic constraints include the ability to withstand shock waves, weather collisions and groundings.
Older ships and pleasure craft often have or had wooden hulls. Steel is used for most commercial vessels. Aluminium is frequently used for fast vessels, and composite material
s are often found in sailboats and pleasure craft. Some ships have been made with concrete hulls
Propulsion systems for ships fall into three categories: human propulsion, sailing
, and mechanical propulsion. Human propulsion includes rowing
, which was used even on large galley
s. Propulsion by sail generally consists of a sail hoisted on an erect mast, supported by stays and spars and controlled by ropes. Sail systems were the dominant form of propulsion until the 19th century. They are now generally used for recreation and competition, although experimental sail systems, such as the turbosail
s, and wingsail
s have been used on larger modern vessels for fuel savings.
Mechanical propulsion systems
generally consist of a motor or engine turning a propeller
, or less frequently, an impeller
or wave propulsion fins
. Steam engine
s were first used for this purpose, but have mostly been replaced by two-stroke
diesel engines, outboard motors, and gas turbine engine
s on faster ships. Nuclear reactors
producing steam are used to propel warship
s and icebreaker
s, and there have been attempts to utilize them to power commercial vessels (see NS ''Savannah''
In addition to traditional fixed and controllable pitch propellers there are many specialized variations, such as contra-rotating and nozzle-style propellers. Most vessels have a single propeller, but some large vessels may have up to four propellers supplemented with transverse thrusters
for maneuvring at ports. The propeller is connected to the main engine via a propeller shaft and, in case of medium- and high-speed engines, a reduction gearbox. Some modern vessels have a diesel-electric powertrain
in which the propeller is turned by an electric motor
powered by the ship's generators.
For ships with independent propulsion systems for each side, such as manual oars or some paddles
, steering systems may not be necessary. In most designs, such as boats propelled by engines or sails, a steering system becomes necessary. The most common is a rudder, a submerged plane located at the rear of the hull. Rudders are rotated to generate a lateral force which turns the boat. Rudders can be rotated by a tiller
, manual wheels, or electro-hydraulic systems. Autopilot
systems combine mechanical rudders with navigation systems. Ducted propeller
s are sometimes used for steering.
Some propulsion systems are inherently steering systems. Examples include the outboard motor
, the bow thruster
, and the Z-drive
Holds, compartments, and the superstructure
Larger boats and ships generally have multiple decks and compartments. Separate berthing
s and heads
are found on sailboats over about . Fishing boats and cargo ships typically have one or more cargo holds. Most larger vessels have an engine room, a galley
, and various compartments for work. Tanks are used to store fuel, engine oil, and fresh water. Ballast tanks are equipped to change a ship's trim and modify its stability.
Superstructures are found above the main deck. On sailboats, these are usually very low. On modern cargo ships, they are almost always located near the ship's stern. On passenger ships and warships, the superstructure generally extends far forward.
Shipboard equipment varies from ship to ship depending on such factors as the ship's era, design, area of operation, and purpose. Some types of equipment that are widely found include:
can be the home of antennas, navigation lights, radar transponders, fog signals, and similar devices often required by law.
* Ground tackle comprises the anchor, its chain or cable, and connecting fittings.
* Cargo equipment such as cranes
and cargo booms may be used to load and unload cargo and ship's stores.
* Safety equipment such as lifeboats
s, and survival suit
s are carried aboard many vessels for emergency use.
Ships float in the water at a level where mass of the displaced water equals the mass of the vessel, such that the downwards force of gravity
equals the upward force of buoyancy
. As a vessel is lowered into the water its weight remains constant but the corresponding weight of water displaced by its hull increases. If the vessel's mass is evenly distributed throughout, it floats evenly along its length and across its beam
(width). A vessel's stability is considered in both this hydrostatic
sense as well as a hydrodynamic
sense, when subjected to movement, rolling and pitching, and the action of waves and wind. Stability problems can lead to excessive pitching and rolling, and eventually capsizing and sinking.
The advance of a vessel through water is resisted by the water. This resistance can be broken down into several components, the main ones being the friction of the water on the hull and wave making resistance
. To reduce resistance and therefore increase the speed for a given power, it is necessary to reduce the wetted surface and use submerged hull shapes that produce low amplitude waves. To do so, high-speed vessels are often more slender, with fewer or smaller appendages. The friction of the water is also reduced by regular maintenance of the hull to remove the sea creatures and algae that accumulate there. Antifouling
paint is commonly used to assist in this. Advanced designs such as the bulbous bow
assist in decreasing wave resistance.
A simple way of considering wave-making resistance is to look at the hull in relation to its wake. At speeds lower than the wave propagation speed, the wave rapidly dissipates to the sides. As the hull approaches the wave propagation speed, however, the wake at the bow begins to build up faster than it can dissipate, and so it grows in amplitude
. Since the water is not able to "get out of the way of the hull fast enough", the hull, in essence, has to climb over or push through the bow wave. This results in an exponential
increase in resistance with increasing speed.
This hull speed
is found by the formula:
or, in metric
where ''L'' is the length of the waterline in feet or meters.
When the vessel exceeds a speed/length ratio of 0.94, it starts to outrun most of its bow wave
, and the hull actually settles slightly in the water as it is now only supported by two wave peaks. As the vessel exceeds a speed/length ratio of 1.34, the hull speed, the wavelength is now longer than the hull, and the stern is no longer supported by the wake, causing the stern to squat, and the bow rise. The hull is now starting to climb its own bow wave, and resistance begins to increase at a very high rate. While it is possible to drive a displacement hull faster than a speed/length ratio of 1.34, it is prohibitively expensive to do so. Most large vessels operate at speed/length ratios well below that level, at speed/length ratios of under 1.0.
For large projects with adequate funding, hydrodynamic resistance can be tested experimentally in a hull testing pool or using tools of computational fluid dynamics
Vessels are also subject to ocean surface wave
s and sea swell
as well as effects of wind
. These movements can be stressful for passengers and equipment, and must be controlled if possible. The rolling movement can be controlled, to an extent, by ballasting or by devices such as fin stabilizers
. Pitching movement is more difficult to limit and can be dangerous if the bow submerges in the waves, a phenomenon called pounding. Sometimes, ships must change course or speed to stop violent rolling or pitching.
A ship will pass through several stages during its career. The first is usually an initial contract to build the ship, the details of which can vary widely based on relationships between the shipowner
s, operators, designers
and the shipyard
. Then, the design phase carried out by a naval architect. Then the ship is constructed in a shipyard. After construction, the vessel is launched and goes into service. Ships end their careers in a number of ways, ranging from shipwreck
s to service as a museum ship
to the scrapyard
A vessel's design starts with a specification, which a naval architect
uses to create a project outline, assess required dimensions, and create a basic layout of spaces and a rough displacement. After this initial rough draft, the architect can create an initial hull design, a general profile and an initial overview of the ship's propulsion. At this stage, the designer can iterate on the ship's design, adding detail and refining the design at each stage.
The designer will typically produce an overall plan, a general specification describing the peculiarities of the vessel, and construction blueprints to be used at the building site. Designs for larger or more complex vessels may also include sail plans, electrical schematics, and plumbing and ventilation plans.
As environmental laws are becoming more strict, ship designers need to create their design in such a way that the ship, when it nears its end-of-term, can be disassembled
easily and that waste is reduced to a minimum.
Ship construction takes place in a shipyard
, and can last from a few months for a unit produced in series, to several years to reconstruct a wooden boat like the frigate ''Hermione'', to more than 10 years for an aircraft carrier. During World War II
, the need for cargo ships was so urgent that construction time for Liberty Ships
went from initially eight months or longer, down to weeks or even days. Builders employed production line and prefabrication techniques such as those used in shipyards today.
Hull materials and vessel size play a large part in determining the method of construction. The hull of a mass-produced fiberglass sailboat is constructed from a mold, while the steel hull of a cargo ship is made from large sections welded together as they are built.
Generally, construction starts with the hull, and on vessels over about , by the laying of the keel. This is done in a drydock
or on land. Once the hull is assembled and painted, it is launched. The last stages, such as raising the superstructure and adding equipment and accommodation, can be done after the vessel is afloat.
Once completed, the vessel is delivered to the customer. Ship launching
is often a ceremony of some significance, and is usually when the vessel is formally named. A typical small rowboat can cost under US$100, $1,000 for a small speedboat, tens of thousands of dollars for a cruising sailboat, and about $2,000,000 for a Vendée Globe
class sailboat. A trawler may cost $2.5 million, and a 1,000-person-capacity high-speed passenger ferry can cost in the neighborhood of $50 million. A ship's cost partly depends on its complexity: a small, general cargo ship
will cost $20 million, a Panamax
-sized bulk carrier
around $35 million, a supertanker
around $105 million and a large LNG carrier
nearly $200 million. The most expensive ships generally are so because of the cost of embedded electronics: a costs around $2 billion, and an aircraft carrier goes for about $3.5 billion.
Repair and conversion
Ships undergo nearly constant maintenance during their career, whether they be underway, pierside, or in some cases, in periods of reduced operating status between charters or shipping seasons.
Most ships, however, require trips to special facilities such as a drydock
at regular intervals. Tasks often done at drydock include removing biological growths on the hull, sandblasting
and repainting the hull, and replacing sacrificial anode
s used to protect submerged equipment from corrosion. Major repairs to the propulsion and steering systems as well as major electrical systems are also often performed at dry dock.
Some vessels that sustain major damage at sea may be repaired at a facility equipped for major repairs, such as a shipyard. Ships may also be converted for a new purpose: oil tanker
s are often converted into floating production storage and offloading unit
End of service
Most ocean-going cargo ships have a life expectancy of between 20 and 30 years. A sailboat made of plywood or fiberglass can last between 30 and 40 years. Solid wooden ships can last much longer but require regular maintenance. Carefully maintained steel-hulled yachts can have a lifespan of over 100 years.
As ships age, forces such as corrosion, osmosis, and rotting compromise hull strength, and a vessel becomes too dangerous to sail. At this point, it can be scuttled
at sea or scrapped
. Ships can also be used as museum ships
, or expended to construct breakwaters
or artificial reef
Many ships do not make it to the scrapyard, and are lost in fires, collisions, grounding
, or sinking at sea. The Allies lost some 5,150 ships during World War II
One can measure ships
in terms of overall length
, length between perpendiculars
, length of the ship at the waterline
, beam (breadth)
, depth (distance between the crown of the weather deck and the top of the keelson), draft
(distance between the highest waterline and the bottom of the ship) and tonnage
. A number of different tonnage definitions exist and are used when describing merchant ships for the purpose of tolls, taxation, etc.
In Britain until Samuel Plimsoll
's Merchant Shipping Act of 1876
, ship-owners could load their vessels until their decks were almost awash, resulting in a dangerously unstable condition. Anyone who signed on to such a ship for a voyage and, upon realizing the danger, chose to leave the ship, could end up in jail
. Plimsoll, a Member of Parliament
, realised the problem and engaged some engineer
s to derive a fairly simple formula
to determine the position of a line on the side of any specific ship's hull which, when it reached the surface of the water during loading of cargo, meant the ship had reached its maximum safe loading level. To this day, that mark, called the "Plimsoll Line
", exists on ships' sides, and consists of a circle
with a horizontal line through the centre. On the Great Lakes of North America the circle is replaced with a diamond. Because different types of water (summer, fresh, tropical fresh, winter north Atlantic) have different densities, subsequent regulations required painting a group of lines forward of the Plimsoll mark to indicate the safe depth (or freeboard above the surface) to which a specific ship could load in water of various densities. Hence the "ladder" of lines seen forward of the Plimsoll mark to this day. This is called the "freeboard mark
" or "load line mark
" in the marine industry
Ship pollution is the pollution of air and water by shipping
. It is a problem that has been accelerating as trade has become increasingly globalized, posing an increasing threat to the world's oceans and waterways as globalization
continues. It is expected that "shipping traffic to and from the United States is projected to double by 2020." Because of increased traffic in ocean port
s, pollution from ships also directly affects coastal areas. The pollution produced affects biodiversity
, climate, food, and human health. However, the degree to which humans are polluting and how it affects the world is highly debated and has been a hot international topic for the past 30 years.
Oil spills have devastating effects on the environment. Crude oil contains polycyclic aromatic hydrocarbons
(PAHs) which are very difficult to clean up, and last for years in the sediment
and marine environment.
Marine species constantly exposed to PAHs can exhibit developmental problems, susceptibility to disease, and abnormal reproductive cycles.
By the sheer amount of oil carried, modern oil tankers must be considered something of a threat to the environment. An oil tanker can carry of crude oil, or . This is more than six times the amount spilled in the widely known ''Exxon Valdez'' incident
. In this spill, the ship ran aground and dumped of oil into the ocean in March 1989. Despite efforts of scientists, managers, and volunteers, over 400,000 seabirds
, about 1,000 sea otters
, and immense numbers of fish were killed.
The International Tanker Owners Pollution Federation has researched 9,351 accidental spills since 1974.
According to this study, most spills result from routine operations such as loading cargo, discharging cargo, and taking on fuel oil.
91% of the operational oil spills were small, resulting in less than 7 tons per spill.
Spills resulting from accidents like collisions, groundings, hull failures, and explosions are much larger, with 84% of these involving losses of over 700 tons.
Following the ''Exxon Valdez'' spill, the United States passed the Oil Pollution Act of 1990
(OPA-90), which included a stipulation that all tankers entering its waters be double-hulled
by 2015. Following the sinkings of ''Erika
'' (1999) and ''Prestige
'' (2002), the European Union
passed its own stringent anti-pollution packages (known as Erika I, II, and III), which require all tankers entering its waters to be double-hulled by 2010. The Erika packages are controversial because they introduced the new legal concept of "serious negligence".
When a large vessel such as a container ship
or an oil tanker unloads cargo, seawater is pumped into other compartments in the hull to help stabilize and balance the ship. During loading, this ballast water is pumped out from these compartments.
One of the problems with ballast water transfer is the transport of harmful organisms. Meinesz
believes that one of the worst cases of a single invasive species causing harm to an ecosystem can be attributed to a seemingly harmless plankton
ic organism . ''Mnemiopsis leidyi
'', a species of comb jelly
that inhabits estuaries from the United States to the Valdés peninsula in Argentina
along the Atlantic
coast, has caused notable damage in the Black Sea
. It was first introduced in 1982, and thought to have been transported to the Black Sea in a ship's ballast water. The population of the comb jelly shot up exponentially and, by 1988, it was wreaking havoc upon the local fishing
industry. "The anchovy
catch fell from in 1984 to in 1993; sprat from in 1984 to in 1993; horse mackerel
from in 1984 to zero in 1993."
Now that the comb jellies have exhausted the zooplankton
, including fish larvae, their numbers have fallen dramatically, yet they continue to maintain a stranglehold on the ecosystem
. Recently the comb jellies have been discovered in the Caspian Sea
. Invasive species can take over once occupied areas, facilitate the spread of new diseases
, introduce new genetic
material, alter landscapes and jeopardize the ability of native species to obtain food. "On land and in the sea, invasive species are responsible for about 137 billion dollars in lost revenue and management costs in the U.S. each year."
Ballast and bilge
discharge from ships can also spread human pathogens
and other harmful diseases and toxins
potentially causing health issues for humans and marine life alike. Discharges into coastal waters, along with other sources of marine pollution, have the potential to be toxic to marine plants, animals, and microorganisms
, causing alterations such as changes in growth, disruption of hormone
cycles, birth defects, suppression of the immune system
, and disorders resulting in cancer
, and genetic abnormalities or even death.
emissions from ships are considered to be a significant source of air pollution
. "Seagoing vessels are responsible for an estimated 14 percent of emissions of nitrogen from fossil fuels and 16 percent of the emissions of sulfur from petroleum uses into the atmosphere."
In Europe ships make up a large percentage of the sulfur introduced to the air, "as much sulfur as all the cars, lorries
and factories in Europe put together".
"By 2010, up to 40% of air pollution over land could come from ships."
Sulfur in the air creates acid rain
which damages crops and buildings. When inhaled, sulfur is known to cause respiratory
problems and increase the risk of a heart attack
Ship breaking or ship demolition is a type of ship disposal
involving the breaking up of ships for scrap recycling
, with the hulls being discarded in ship graveyard
s. Most ships have a lifespan of a few decades before there is so much wear that refitting and repair becomes uneconomical. Ship breaking allows materials from the ship, especially steel, to be reused.
In addition to steel and other useful materials, however, ships (particularly older vessels) can contain many substances that are banned or considered dangerous in developed countries
and polychlorinated biphenyls
(PCBs) are typical examples. Asbestos was used heavily in ship construction until it was finally banned in most of the developed world in the mid 1980s. Currently, the costs associated with removing asbestos, along with the potentially expensive insurance and health risks, have meant that ship-breaking in most developed countries is no longer economically viable. Removing the metal for scrap can potentially cost more than the scrap value of the metal itself. In most of the developing world, however, shipyards can operate without the risk of personal injury lawsuits
or workers' health claims
, meaning many of these shipyards may operate with high health risks. Furthermore, workers are paid very low rates with no overtime or other allowances. Protective equipment is sometimes absent or inadequate. Dangerous vapors and fumes from burning materials can be inhaled, and dusty asbestos-laden areas around such breakdown locations are commonplace.
Aside from the health of the yard workers, in recent years, ship breaking has also become an issue of major environmental concern
. Many developing nations, in which ship breaking yards are located, have lax or no environmental law
, enabling large quantities of highly toxic materials to escape into the environment and causing serious health problems among ship breakers, the local population and wildlife. Environmental campaign groups such as Greenpeace
have made the issue a high priority for their campaigns.
* Admiralty law
* Auxiliary ship
* Chartering (shipping)
* Dynamic positioning
* Environmental impact of shipping
* Factory ship
* Flag state
* Glossary of nautical terms
* Marine electronics
* Marine fuel management
* Maritime history
* Mother ship
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* Naval ship
* Nuclear marine propulsion
* Sailing ship
* Ship burial
* Ship transport
* Train ferry
* Vessel safety survey
* Ship model
* Ship model basin
* Ship replica
* List of fictional ships
* List of historical ship types
* List of Panamax ports
* List of largest cruise ships
* List of world's largest ships by gross tonnage
* List of world's longest ships
* Lists of ships
* Lists of shipwrecks
* Maersk Triple E class
* Ultra Large Crude Carrier
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