cofferdam

Plural: cofferdams

Noun

• large watertight chamber used for construction under water
• A temporary watertight enclosure used to create a dry foundation for building bridges and other structures over water.
• An empty space that acts as a protective barrier between two floors or bulkheads on a ship.
• A rubber dam to keep the teeth dry when operating upon them.

Synonyms

caisson, pneumatic caisson