Have you seen Ghosts of the Abyss? It's the documentary James Cameron made during/after filming Titanic. For ROV enthusiasts out there, it's a must see.
The ROVs used in the film, Jake and Elwood, have some pretty incredible features - here's more info on the SpiderBot.
David L (not me) is currently working on an alternative to the fiber optic slip ring used on this type of ROV. You can read more about his project and comment on the forum discussion here.