It wouldn't really make sense for all water types to be able to breathe underwater, since there's some that are based on things that can't. Even something like Kyogre would need air, being based on a whale. I imagine they'd all be able to hold their breath a really long time, though, but eventually they just have to breathe, like this poor oshawott here. Luckily he's not very far down, so I'm sure he'll be fine.
Also includes versions with just text, just inhaling lines, and neither.