A watercraft may have a shaped charge and a gas chamber. The gas chamber may be adjacent to the shaped charge in a direction of action of the shaped charge. The gas chamber can be varied in length in the direction of action of the shaped charge. Further, the shaped charge may be movable parallel to the direction of action of the shaped charge. A threaded rod can be used to move the shaped charge. In some cases a length of the gas chamber is variable between 0.1-times and 10.0 times a diameter of the shaped charge. The watercraft may be configured in some instances as an unmanned underwater vehicle.