_The prototype robot fish looks a bit like a hand grenade, far cruder than other robotic swimmers we've seen that are designed to monitor pollution or lake algae. But verisimilitude doesn't seem to be important for leadership. Porfiri and other scientists have observed that what distinguishes fish leaders is that they swish their tails faster, circle around, and accelerate to gather a school, and then lead it. Porfiri modeled the behavior of bait fish based on the principles of fluid dynamics. He guessed that since schooling fish swim with different species varying in appearance and size, they would accept a robotic leader that was larger than themselves.