I've just encountered a creature that genuinely resembles a fish and it made me realize something: They kind of swim like fish with a swim bladder disease. I have had a number of creatures that would have been practically graceful if it weren't for their complete inability to stay upright so I'm wondering if a creatures only control over its orientation is entirely down to its muscle movements? And if so, would it be a good idea to implement some means for them to evolve a swim bladder that would help them to right themselves like a real fish would have?