Propellers are good for moving a boat through water, but they’re noisy and stress out marine animals, making them a suboptimal solution for a vessel trying to film a natural ecosystem. To solve the problem, scientists have built a four-finned robot that mimics the graceful swimming of a cuttlefish (seen above). New Scientist reports that the robot (named Sepios) is nearly silent and that its fins don’t get tangled in aquatic plants.