A method and apparatus for stopping an impeller-driven watercraft is includes distributing a plurality of submunitions in advance of a path of the impeller-driven watercraft. Each of the submunitions includes a buoyant member, a first end cap, and a second end cap; the second end cap is heavier than the first end cap. A lanyard connects the first end cap to the second end cap, optionally passing through the buoyant member. At least one of the submunitions enters an intake vent of the impeller-driven watercraft and attaches to a blade of an impeller of the impeller-driven watercraft, causing cavitation and imbalance, thereby slowing the impeller-driven watercraft.