Quote Originally Posted by remetagross View Post
Can they breathe water?
Absolutely. Actually, they technically, as written, cannot breathe air. But that's mostly because WotC never understood how their own subtypes work. (Aquatic) in particular makes no sense. By RAW and by itself, it does not give the ability to breathe air and requires the Amphibious quality for it. However, a creature like the Fossergrim or the scrag, depicted as living in shallow waters, interacting with landbound creatures and having human-like anatomy, are Aquatic but not Amphibious. To go even further, a whale can, by RAW, breathe underwater but not outside it, the exact opposite of real life.
In this thread, I always consider, if I don't have a reason to think otherwise, that all creatures with the Aquatic subtype can breathe both air and water, it's the only way to make it make sense.