A moon pool is a feature of marine drilling platforms, drillships and diving support vessels, some

marine research Oceanography (), also known as oceanology and ocean science, is the scientific study of the oceans. It is an Earth science, which covers a wide range of topics, including ecosystem dynamics; ocean currents, waves, and geophysical fluid dyna ...

and underwater

exploration Exploration refers to the historical practice of discovering remote lands. It is studied by geographers and historians. Two major eras of exploration occurred in human history: one of convergence, and one of divergence. The first, covering most ...

research vessel A research vessel (RV or R/V) is a ship or boat designed, modified, or equipped to carry out research at sea. Research vessels carry out a number of roles. Some of these roles can be combined into a single vessel but others require a dedicate ...

s, and underwater habitats, in which it is also known as a wet porch. It is an opening in the floor or base of the

hull Hull may refer to: Structures * Chassis, of an armored fighting vehicle * Fuselage, of an aircraft * Hull (botany), the outer covering of seeds * Hull (watercraft), the body or frame of a ship * Submarine hull Mathematics * Affine hull, in affi ...

, platform, or chamber giving access to the water below, allowing technicians or researchers to lower

tool A tool is an object that can extend an individual's ability to modify features of the surrounding environment or help them accomplish a particular task. Although many animals use simple tools, only human beings, whose use of stone tools dates b ...

s and instruments into the sea. It provides shelter and protection so that even if the

ship A ship is a large watercraft that travels the world's oceans and other sufficiently deep waterways, carrying cargo or passengers, or in support of specialized missions, such as defense, research, and fishing. Ships are generally distinguished ...

is in high seas or surrounded by ice, researchers can work in comfort rather than on a deck exposed to the elements. A moon pool also allows divers, diving bells, ROVs, or small submersible craft to enter or leave the water easily and in a more protected environment. Moon pools can be used in chambers below sea level, especially for the use of

scuba diver Scuba diving is a mode of underwater diving whereby divers use breathing equipment that is completely independent of a surface air supply. The name "scuba", an acronym for " Self-Contained Underwater Breathing Apparatus", was coined by Chr ...

s, and their design requires more complex consideration of air and water

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country a ...

acting on the moon pool surface.

First use in oil drilling at sea

Moon pools originated in the oil drilling industry, which uses them in drilling at sea or in lakes, to pass drilling equipment into the water from a platform or drillship. Drill pipes need to run vertically through the structure or hull, and the moon pool provides the means to do this.

The Glomar Explorer

The Hughes Glomar Explorer was a , ship constructed by the United States in the early 1970s for the recovery of a sunken Soviet submarine from the Pacific seabed. The ship's design was broadly inspired by oil drilling ships and included a moon pool measuring , into which the submarine was to be recovered, with the bottom of the moon pool then closed off by two gates that would allow the recovered vessel to be examined under cover and in dry conditions. This was a singular use of a moon pool and also possibly the largest dedicated moon pool constructed to date.

In underwater habitats

Very deep moon pools are used in underwater habitats—submerged chambers used by divers engaged in underwater research,

marine salvage Marine salvage is the process of recovering a ship and its cargo after a shipwreck or other maritime casualty. Salvage may encompass towing, re-floating a vessel, or effecting repairs to a ship. Today, protecting the coastal environment from s ...

, and

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. In this case, shown in part D of the diagram, there is no dry access between the chamber and the sea surface, and the moon pool is the only entry or exit to the chamber. Submerged chambers provide dry areas for work and rest without the need to ascend to the surface. This kind of submerged chamber uses the same principles as the

diving bell A diving bell is a rigid chamber used to transport divers from the surface to depth and back in open water, usually for the purpose of performing underwater work. The most common types are the open-bottomed wet bell and the closed bell, which c ...

, except they are fixed to the seafloor and may be called a wet porch, wet room, or wet bell. Sometimes the term moon pool is used to mean the complete chamber, not just the opening in the bottom and the air–water interface. The alternative to a moon pool in an underwater habitat is the lock-out chamber, which is essentially like a fixed

submarine A submarine (or sub) is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely op ...

, maintaining internal air pressures lower than ambient sea pressure down to one

atmosphere An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A ...

, with an airlock to enable entry and exit underwater. Underwater habitats may have connected chambers with moon pools and lock-out chambers.

Examples of underwater habitats with moon pools

* SEALAB II (US Navy) * The Florida laboratory

Aquarius Aquarius may refer to: Astrology * Aquarius (astrology), an astrological sign * Age of Aquarius, a time period in the cycle of astrological ages Astronomy * Aquarius (constellation) * Aquarius in Chinese astronomy Arts and entertainment ...

, where it is called a wet porch

Gallery of types

Catamaran moon pool.png, Cross-section of an open moon pool above the waterline, in a catamaran or a semi-submersible platform Waterline moon pool.png, An open moon pool at the waterline, in a ship or floating structure Airlock moon pool.png, A moon pool below the waterline in an airtight chamber, in a ship or floating structure Chamber moon pool.png, A moon pool below the waterline in an airtight submerged chamber

References