Blue Planet (probably not with its native system)
I think Blue Planet is a fascinating setting that would be tremendous fun to explore. I'd like to play it, but probably not in its native system. Though there is a free 3rd edition starter out now, so maybe the rules are better. SW feels like it might work; RIFTS showed that it can handle some actually powerful PCs, so having cetaceans should be a cinch—even an orca, for all its power, is not the biggest fish in the Poseidon sea, and comes with plenty of drawbacks to balance it out.
Heavy themes of exploration, mystery, and the majestic, frightening, alien power of the deeps with all the secrets it holds sounds good to me.
Anyone else?