围堰;潜水箱
Cofferdam \Cof"fer*dam\, n. A water-tight inclosure, as of piles packed with clay, from which the water is pumped to expose the bottom (of a river, etc.) and permit the laying of foundations, building of piers, etc.
cofferdam n : large watertight chamber used for construction under water [syn: {caisson}, {pneumatic caisson}]