Drones: they're not just for the sky anymore. DARPA is seeking compact deep-ocean autonomous craft developed faster, smaller, and cheaper than today's full-ocean-depth AUV systems. DARPA's Deep Thoughts program , for which the agency issued a solicitation on Thursday, is looking to change the autonomous undersea vehicle (AUV, not to be confused with unmanned aerial vehicles, or UAVs) paradigm by developing a new generation of compact AUVs that can reach full-ocean depths "at a fraction of the size of current state-of-the-art AUV systems."  Deep-ocean exploration has to contend with plenty of challenges, intense water pressure chief among them, which makes successful seafloor-capable craft - manned or unmanned - difficult, slow, and expensive to build. Those sticking points are what DARPA hopes to address.…