46 CFR 169.231 - Definitions relating to hull examinations.
As used in the part -
(a) Drydock examination means hauling out a vessel or placing a vessel in a drydock or slipway for an examination of all accessible parts of the vessel's underwater body and all through-hull fittings, sea chests, sea valves, sea strainers, and valves for the emergency bilge suction.
(b) Underwater survey means the examination of the vessel's underwater hull including all through-hull fittings and appurtenances, while the vessel is afloat.
(c) Internal structural examination means an examination of the vessel while afloat or in drydock and consists of a complete examination of the vessel's main strength members, including the major internal framing, the hull plating, voids, and ballast tanks, but not including cargo or fuel oil tanks.