, a vessel's freeboard
is the distance from the waterline
to the upper deck
level, measured at the lowest point of sheer
where water can enter the boat
In commercial vessels, the latter criterion measured relative to the ship's load line
, regardless of deck arrangements, is the mandated and regulated meaning.
In yachts, a low freeboard is often found on racing boats
, for increased speed (by reducing weight and therefore drag). A higher freeboard will give more room in the cabin
, but will increase weight and drag, compromising speed. A higher freeboard, such as used on ocean liners
, also helps weather waves and so reduce the likelihood of being washed over by full water waves on the weather deck
. A low-freeboard boat is susceptible to taking in water in rough seas. Freighter ships and warship
s use high freeboard designs to increase internal volume, which also allows them to satisfy International Maritime Organization
(IMO) damage stability regulations, due to increased reserve buoyancy
*For the term as used in measuring sea ice, see Sea ice thickness
, a type of vessel that often is a surface ship with a very low freeboard.