cofferdam
cof.fer.dam \-.dam\ n 1: a watertight enclosure from which water is pumped to expose the bottom o f a body of water and permit construction (as of a pier) 2: a watertight structure for making repairs below the waterline of a ship
cof.fer.dam \-.dam\ n 1: a watertight enclosure from which water is pumped to expose the bottom o f a body of water and permit construction (as of a pier) 2: a watertight structure for making repairs below the waterline of a ship