If it works as stated, this sea drone will be more than just a pool toy. The 16 pound, two-foot-long sub can dive down to 26 feet beneath the surface of the water, and can travel at speeds of about 2 mph for about 50 minutes. Because radio signals have a harder time traveling through salty water, the seawater version uses a different signal frequency than the freshwater one, and can also be controlled through a tether cable instead of remotely.