The amazing phenomenon in which a trout can hang motionless in the stream of a waterfall has been known for a long time, but to date, no explanation has been found for it. From the side of the water flowing around the trout's body, a force acts on the trout that balances its weight. A similar force occurs when a trout moves in still water at the speed of water in a waterfall. Since the trout is subject to a suction force in the direction of its movement, equal to its weight, a school of such trout can be connected to the vessel, just as horses are harnessed to a carriage. To implement this idea, you must first understand where the trout will get the energy to move the vessel. It is now known that this is nuclear energy that the trout extract from the water. Thus, the trout can be considered as a mover, converting nuclear energy extracted from the water into a force capable of pulling the mover in the direction of its movement. The conditions under which such a situation is possible in shipping are given. Unlike other known proposals for fuel-free engines, which must receive experimental confirmation, the engine in question already has experimental confirmation in the form of a reliably established natural phenomenon. The only problem is understanding the laws responsible for the existence of this phenomenon and their subsequent use in practice.
V. P. Torchigin (2026) studied this question.