Abstract: A device for making waves in a liquid (2) contained in a pond (1) such as a swimming pool, by the substantially vertical reciprocating motion of a body placed within the liquid or at the surface thereof. The body is a shell (3) capable of being filled with the said liquid (2). The shell (3) is connected by a linking member (4) to an element capable of periodically applying an upward-oriented force in a substantially vertical direction, then in lowering the said shell (3) again. The shell (3) preferably comprises a horizontal base and substantially vertical side walls.