PURPOSE: To make a beginner learn the optimum yacht sailing technique through experiences acquired by himself alone by providing the 1st sensor which detects the force in the back and forth direction of a yacht body and controlling a water current producing by device by means of the signal of the sensor.

CONSTITUTION: When a wind 3 is acted on the sail 1 of a yacht body 2 moored in a water tab 11 from an air blowing device 14, driving force F5 which acts on the yacht body as the force is back and forth direction is produced and a sensor detects the driving force. A water current producing device 12 is controlled by means of the signal of the sensor. When a water current acts on the yacht body 2, reaction force F6 is produced, but control is made so that the reaction force F6 and F5 offset each other to zero. Therefore, a beginner can learn the optimum angle while the experiences sailing on the yacht body 2 by changing the angle of the sail 1 against the direction of the wind 3.