They killed the WoD off though, which was a damn shame, I'd of loved to have seen a VtM game this gen.
There is a WoD MMO being developed, so keep your hopes up! I loved VTM:bloodlines, never played the tabletop but its a great universe... http://pc.ign.com/articles/122/1221543p1.html
On topic though,
I think its generally accepted that "lesser" undead (zombies, skeletons, etc) can live in aerobic environments, but more "advanced" undead (liches, vampires) require some level of an atmosphere.
Another thing to think of is maybe vampires get waterlogged when underwater too long, so just like humans, the lung space (and rest of body cavity) fill with water, making it harder to surface.