Cofferdam
a water-tight inclosure in a body of water, prepared to expose the bottom for laying a foundation for a pier, abutment or quay. It consists of wooden piles packed with clay, etc., or steel sheet piles driven around an interior framework.
COFFER FISH (Ostracion), a peculiar genus of bony fishes in the small order Plectognathi, and in the family Sclerodermi, which also includes the file-fishes. The body is inclosed in a firm box formed of hexagonal bony scales fitted into one another like a mosaic. The best known form is O. quadricornis from the tropical Atlantic.