A team of researchers from MIT and Harvard were surprised when accidentally discovered this phenomenon. They are studying how a live trout preserves its energy by swimming behind barriers against water stream, and unwittingly placed a dead fish in the experimental setup. The fish was moving against the tide that pushed backwards, making slow progress until they reached the barrier and pushed back the influence of power. Researchers found nothing special in this, until they realized that the fish were already dead. as evidenced, Objects that block the natural flow of water, such as a rock or a boat, creating a series of complex turbines in power as the water is directed after the obstacle. In some cases, the turbine array formed behind a barrier forcing the body and tail of the fish coming in coordination. This tilts the body in such a way that the vortices, causing pressure drop, to apply a suction force that propels the fish forward. This is the way in which fish save energy, and with a little push from their bodies, proceed or stop.