Not all deep sea fish are bizarre and otherwordly. Some are not so different from fish seen in much shallower waters. For instance, the black swallower is a very average-looking fish, though its skin is closer to brownish-black than straight black. Its most noteworthy feature is its ability to swallow prey larger than itself, thanks to its articulated jaw and its very distendable stomach.
Just why Aquatica Abyssus decided to uplift a black swallower was hard to say. Perhaps they were attempting to make their repertoire as well-rounded as they could. Not everyone who wanted to dive down to the dark depths wants to become an Animalian with a very odd body design or a hermaphrodite.
Statistically speak, finding a black swallower shouldn't have been hard considering they're a very common fish and widespread fish. The hard part was that its small size of 6-8 inches and its dark coloration made it hard to spot in its natural habitat. The main reason that the black swallower that would come to be named Wallaby (named for his pouch-like stomach) was found was because he recently eaten a large meal. Fortunately, the meal was already dead and didn't uplift with Wallaby.
Wallaby (or Wally as he was often called) wasn't as big and impressive as some of the other fish Animalians like the shark. He was only average at best in size compare to humans. His chest and stomach weren't as flabby as one might expect, but the skin on them could stretch out quite considerably.
Of course, while education helped Wally catch up on the human world, habits and instincts are harder to fight. Down in the abyssal depths, finding food isn't easy. As such, deep sea fish will eat as much as they can find for they're never sure when they'll find their next meal. Part of this carried over with their uplifting into Animalians. It's not that they were constantly hungry, but when present with a large amount of food, like a Thanksgiving buffet, they can't help but gorge themselves on more than they should.
Beacon was kicking hirself for not remembering what happened last time. Shi should have remembered that it took a lot of food to make hir feel full, more than shi actually needed to eat. Now shi and hir mate were all bloated out from Thanksgiving, but at least they had company. Gulf and Wally had also overindulged. Apparently no one remembered to tell them that they didn't need to eat all that they could. Wally was possibly the worst off considering he was used to eating several sizes his own weight. At least the weight loss classes should help them get rid of their bulging bellies.