China just revealed a surveillance drone that looks and moves like a real fish Instead of a propeller, it's basically a bendy tail with three joints that's an important design choice, because underwater drones often get detected by the sound of their propellers It runs autonomously for about five hours and uses sonar to navigate It only goes five meters deep which sounds like a limitation, until you realize that's exactly where the valuable ports, cables and dams are. And you can drop a…