PURPOSE: To efficiently carry out ultra-low altitude flight, etc., accompanied by a ground effect by providing a main wing in the vicinity of the center of gravity of a plane body, providing small wings in the front and rear of the main wing and providing wing end plates which extend out downwards on both end portions of these wings respectively.

CONSTITUTION: In a water surface plane, a main wing 4 is provided on the center portion in the longitudinal direction of a center body 2 while providing a front wing 6 and a tail wing 8 in the front and rear thereof. The center of gravity G of the body is placed a little to the front of the mean aerodynamic chord length of the main wing 4. Wing end plates 12, 20 are extended out downward at a right angle from both end portions of the main wing 4 and tail wing 8 respectively. The heights H from the bottom ends of the wing end plates 12, 20 to the water surface are set to be nearly equal to each other in the normal navigating posture of the body. Thereby, both IGE flight accompanied by a ground effect along the water surface, etc., and OGE flight which is separated from the water surface without being accompanied by the ground effect can be efficiently carried out.