Just when you thought it was safe to go back in the water, an anonymous reader writes in with news about a giant robot jellyfish. As if there weren't enough real jellyfish around to trigger our thalassophobia, researchers at Virginia Tech have created Cryo -- an eight-armed autonomous robot that mimics jelly movement with the help of a flexible silicone hat. The man-sized jellybot altogether dwarfs previous efforts, hence the upgrade from small tank to swimming pool for mock field tests. And unlike the passively propelled bots we've seen recently, Cryo runs on batteries, with the researchers hoping to better replicate the energy-efficient nature of jelly movement to eventually increase Cryo's charge cycle to months instead of hours. That's also the reason these robotic jellyfish are getting bigger -- because the larger they are, the further they can go."