To kill one, you must dismember it completely—or inject it with poisonous (to them) bile salts. Instead of braaains, these zombies munch coral, and off the coast of Australia, infestations of the beasts are damaging the Great Barrier Reef at an alarming rate. Enter COTSbot. In development since late 2014, the underwater droid identifies and assassinates the ravenous stars—autonomously. Unlike a human diver, the COTSbot can work safely in rough seas for eight hours at a time and doesn't ask for a paycheck. The machine uses an acoustic sensor to navigate the reef and a camera to identify its prey from afar with 99 percent accuracy. "Very few underwater robots do onboard image processing," says Matthew Dunbabin, the bot's inventor and principal research fellow at the Institute for Future Environments at Queensland University of Technology. "It processes information in real time and takes action."