My pair of Tentacled snakes, Erpeton tentaculatum) these snakes, unlike others.. will actually anticipate the movement of their prey (fish) as they attempt to escape, by moving their body posterior they create a ripple, a disturbance in the water. Setting up for the fish's escape reflex. Grabbing the fish by the head most of the time and injecting it with their fast-acting venom from their rear-fangs (not medically significant to humans). Basically these guys trick fish to escape in the wrong direction. Tentacles are used for sensing for prey, predators in the water.