FearMonkey
Vault Senior Citizen
I'm thinking one of the DLC's will be underwater. Harpoon gun and underwater ruins lead me to believe this.
Possible, but then they would have to either retcon the water to be not so radioactive or force you to take a perk. Or come up with some silly phlebotinum McGuffin to allow you to dive underwater without penalties. Because there's no way Bethesda would let anything inconvenience you while you explore underwater.
Teleport thingies? Underwater Power Armor?
Power armour already lets you breathe underwater for a bit longer, maybe they'll add a mod like an underwater jetpack...
There no rebreather in FO4 like there is in New Vegas?