A ship has a water flow forming path (3) formed in a bottom (2), and a propeller (6) disposed in the path (3) and a rudder (8) on a rear side of the propeller (6). A movable side of the rudder (8) faces toward a bow (1a). As a result of this, thrust increases due to generation of a rapid stream by the propeller (6) in the path (3), the propulsion performance improves and the steering performance improves because the rapid stream in the path (3) acts on the rudder (8). An outboard motor (14) may be provided with a vertical channel (13) in a stern (4) of the boat. Replacement can be made through the vertical channel (13). As the propeller (6) of the outboard motor (14) is recessed, it is possible to pull the boat onto the beach while leaving the outboard motor (14) as it is.