Like its ancient Greek namesake, the Hydra is a monster capable of springing multiple heads from a single body. But while the ancient Greek critter simply grew new serpentine heads, DARPA's Hydra will be a little more versatile.
Being an unmanned submarine itself, Hydra will easily be capable of launching other, smaller Unmanned Underwater Vehicles (UUVs). But the real kicker is the Hydra's capability to launch Unmanned Aerial Vehicles (UAVs). Any target of the Hydra's assault could very rapidly find itself surrounded not only by a school of water-bound robo-subs, but also a flock of their airborne brethren.