Will swimming be the next jump?
For real, I'm actually not a huge fan of underwater travel. I'm level 80 in GW2, and I avoid underwater fighting like the plague. It's just not nearly as much fun as fighting on land. I kind of like being able to swim, but I really don't like underwater combat.
And that said, there's something about swimming underwater in a full suit of armor, without ever running out of breath, that really doesn't fit well with immersion. I'm totally happy with being able to wade a bit into deep water, but not actually going under. If they ever do implement underwater areas, then I hope it's done in a way that's realistic (and without annoying underwater combat).