To reduce excess water in a barge by unloading only sediment, by discharging water in a grab bucket of grabbing together with the sediment.

This sealed grab bucket includes an upper closing cover 20 for closing its upper side opening part in a grabbing state of both shells 1, and is formed so that both shells 1 are operated for opening-closing by vertically operating a lower frame 5 to an upper frame 8 by an opening-closing operation means. The upper closing cover 20 is rotatably installed at its base end side on the arm connecting side of the shells in an upper opening in the grabbing state of the respective shells. and connects a part between an upper surface of the respective upper closing covers 20 and an arm 7 by an interlocking link 22, and is formed so that its tip abuts on each other in a grabbing operation completing state by respectively downwardly rotating both upper closing covers 20 in closing direction side operation of both shells 1.