A UAV developed by a Johns Hopkins University Applied Physics Lab team can stay underwater for months, waiting out of sight until it's called to duty. When the machine does get deployed, it can swim up and fly into the air, just like any other quadcopter. The team calls their creation the
KRAKENS CRACUNS or Corrosion Resistant Aerial Covert Unmanned Nautical System, made using additive manufacturing (3D printing) and other techniques. It can stay submerged hundreds of feet beneath the water's surface, thanks to its composite airframe that can withstand the pressure.