PURPOSE: To eliminate buoyant body to be equipped in the boat by making shell of a horn prepared to the bow or stern of the ship to water tight to make it buoyant.

CONSTITUTION: A horn 2 is projectingly installed to the bow of a boat 1, and the horn 2 consists of a shell 21 formed as one body with the shell 3 of the boat by PRP (fiber reinforced plastics), foamed material 20 filled in it, and a cover 22 closing the upper opening, and is structured to water tight, and has function of buoyant body having large buoyancy. Therefore, the buoyant body to be installed in the ship having been considered necessary for the safety can be eliminated by use of vuoyancy of the horn 2, and so much can increase the space in the ship and utilize it.