A ship (1) includes a hull (2) having side shells (3A, 3B) formed at both sides in athwart ship direction, a pair of watertight compartments (6A, 6B) installed along the side shells (3A, 3B) of both sides in the athwart ship direction in the hull (2) and portions of which are divided and formed by the side shells (3A, 3B), a connection section (7) configured to bring the pair of watertight compartments (6A, 6B) in connection with each other, an opening/closing valve (8) installed at the connection section (7), and a control device (9) configured to control the opening and closing of the opening/closing valve (8), wherein the control device (9) switches the opening/closing valve (8) in an open state into a closed state when a predetermined condition is satisfied after receiving a signal indicating damage to the side shell (3A) has occurred.