Namely, Roper answers our burning questions on fire-based powers underwater and breathing mechanics. A pill developed by the in-game faction called UNTIL will allow heroes to breath with ease and for the sake of fun. Who wants to resurface every five or ten minutes, anyhow?
And as for the water-unfriendly powers, Cryptic is simply taking the "this is a comic book-based world" approach and not messing with anything. However, travel powers apparently aren't going to work underwater, which makes sense. We only hope there's some way to compensate people who spend some time underwater. Giving out a water propeller backpack after completing the first few quest chains couldn't hurt.
