To provide a watercraft capable of quickly assembling and disassembling, capable of relatively reducing a cost and weight, having rigidity for preventing deflection, superior in operability, and easy in a movement in various water states.

This watercraft is composed of an inflatable skin 12 for forming a hull shape at inflating time, and a frame 14 having an extensible rigid keel member 16 for forming a rigid keel shape 41 in the skin, tensioning the skin, and engageable with the skin. The frame has chains or gunnel stiffeners 36, 38, 40, and 42 extending in the vertical direction along or upward to port and starboard side surfaces of the inflatable skin, and joinable to the keel member. The inflatable skin has bow and stern connectors 13 and 15 for respectively connecting the skin to the frame in the bow 19 and the stern 21 of the watercraft 10. The frame 14 forms the upward bending rigid keel shape 41 in the bow and the stern at extending time, and can allow a long draft line and a further faster watercraft.