Reading this article about Lockheed Martin's new "Marlin" AUV, it was interesting to see why this AUV was so effective.
It didn't place the emphasis on the speed or technical capabilities of the AUV, it seemed like it was useful because of the 3D maps it generated. As always, I can't help but imagine 100 OpenROVs that could stitch together a similar model. The available and accessible 3D modeling software, Autodesk's 123D Catch and others, is improving just as quickly as the electronics (Beaglebone and Raspberry Pi, for example).
Now we just need to add the appropriate sensor packages to turn OpenROV into an OpenAUV ;)