Denmark's Supportive Robotics, however, is developing one that's a bit different. Known as Allec, it can be piloted via remote control, but it can also perform its own autonomous missions.

In remote-control mode, Allec is hooked up to a Wi-Fi-equipped buoy via a 30-m (98-ft) electrical cable. That buoy is towed along at the surface, wirelessly sending and receiving signals to and from the user. Utilizing an iOS/Android app on their mobile device, the user controls Allec in real time, and views live video from an onboard 1080p/30fps video camera.

In autonomous mode, the buoy doesn't need to be used. Instead, Allec follows a preprogrammed "flight path," much like many aerial drones are able to do. Whereas they use GPS, though, Allec goes with a dead reckoning system – this means that it uses a compass and an inertial measurement unit (an accelerometer/gyroscope/magnetometer combo) to keep track of how far it goes, and in what directions.