So we have water in this game, right? Infact, we have lots of it. Loads. And we can dive underwater... without needing to rise up to the surface again? Unrealistic.
Ok so the subject says it all. Like us, real life felines and canines cannot breathe underwater. So, there should be a limit.
In character creation, there should be a box that you can tick to say if your character can breathe underwater, because there could be a fictional feline or canine that can breathe underwater. This is just an idea, obviously.