To form simulated waves for which what kind of waves is to be generated can not be predicted by installing a fluid jetting mechanism for forming a swell in the advancing direction and width direction of the waves at the lower part of a flexible sheet.

The flexible sheet 1 is constituted of a material such as rubber and vinyl or the like and the fluid jetting mechanism is constituted of an air compressor 2, a pressure tank 3, an air supply pipe 4 and plural branching pipes 4a-4e branched from the air supply pipe 4. Then, solenoid valves 5a-5e are provided in the middle of the branching pipes 4a-4e and the tips of the branching pipes 4a-4e are made in a nozzle shape, opened upwards and arranged in the width direction and over the entire play water path. A control mechanism 6 controls the valves 5a-5e and controls the selection of the branching pipes 4a-4e and the jetting amount of air. A user rides on a vehicle 7 such as a boat or the like, the air having various kinds of pressure from the branching pipes 4a-4e is blown from a lower part toward the flexible sheet 1 and a game is performed while moving the flexible sheet 1 in a wave shape and moving it in multi-axial directions.