Draft (hull)

The draft or draught of a ship is a determined depth of the vessel below the waterline, measured vertically to its hull's lowest—its propellers, or keel, or other reference point.

[2] A ship's draft/draught is the "depth of the vessel below the waterline measured vertically to the lowest part of the hull, propellers, or other reference point".

[1] That is, the draft or draught is the maximum depth of any part of the vessel, including appendages such as rudders, propellers and drop keels if deployed.

[citation needed] The related term air draft is the maximum height of any part of the vessel above the water.

[citation needed] Draft determines the minimum depth of water a ship or boat can safely navigate in relation to the under keel clearance available.

[citation needed] The draft can also be used to determine the weight of cargo on board by calculating the total displacement of water, accounting for the content of the ship's bunkers, and using Archimedes' principle.

A fully laden ship (with a large draft) can have either a high or low stability, depending on the height of the center of gravity, which is affected by the distribution of cargo.

The draft of a ship can be increased by longitudinal motion in shallow water, a hydrodynamic effect known as squat, which causes a local pressure reduction under the vessel.

It is used in navigation to avoid underwater obstacles and hitting the ocean floor, and as a standard point on the submarine for depth measurements.