Shear wave generator for use subsea, comprising: an excitation unit (1) that is fastened to a top plate (2); a skirt (3) that at an upper end (3a) is fastened sealingly to the top plate and extending downward to an open lower end (3b) of the skirt, such that the top plate and skirt form a closed space by lowering to the seabed; and a pump (5) arranged with fluid communication between said space and the surroundings, such that by pumping water out of said space underpressure is formed acting to suck the shear wave generator fixedly to and partly into the seabed, and by pumping water into said space overpressure is formed acting to lift the shear wave generator up from the seabed. The shear wave generator is distinguished in that the skirt (3) is formed with larger outer diameter or width at its upper end than at its lower end.