Caisson

a structure used in underwater work, consisting of an airtight chamber, open at the bottom and containing air under sufficient pressure to exclude the water.

a boatlike structure used as a gate for a dock or the like.

Nautical .

Also called camel , pontoon. a float for raising a sunken vessel, sunk beside the vessel, made fast to it, and then pumped out to make it buoyant.

a watertight structure built against a damaged area of a hull to render the hull watertight; cofferdam.

a two-wheeled wagon, used for carrying artillery ammunition.

an ammunition chest.

a wooden chest containing bombs or explosives, used formerly as a mine.

Architecture . coffer ( def. 4 ) .

noun

box , case , chamber , chest , float , wagon