Why is Shark so dumb? The Doylist explanation is that Dumb Muscle antagonists are a standard trope in children's animation, but as one fan site pointed out, it could also be that Shark is by far the largest enhanced fish and a standard dose of potion may have a smaller effect on him.
How did the fish kids get out of the cage? Sasha got the keys. How did Sasha get free? A heavy stone block fell on her harness, breaking it. Why did the block fall? Because a chain of eels linked into a rope let go of each other. Why did they let go of each other? Because Shark ordered them to clap for Joe. Joe would never have been defeated if not for his own hubris.
There’s some delicious irony in the fact that the kids manage to get the esca of an anglerfish, which draws in other fish with its lighted lure and has a name that literally means “fisherman fish”, by luring it in with a worm on a string.
Fridge Horror
Joe's near human corpse (After being tricked by Fly) is left there in the ocean to rot. Imagine some unsuspecting fisherman just caught his horrid corpse in his net!
Cryptozoologists would probably insist he was a merman or something.
He'd probably be logged as a drowned John Doe and forgotten about.
What has become of Joe's empire now that their leader is dead?
A popular WMG is that Professor Mackrill reversed the effects of the antidote offscreen (perhaps by pouring large doses of the fish potion into the nearby waters), but this opens up a new can of Fridge Horror when you think about it from the fishes' perspective. Imagine suddenly awakening to sapience, and then having it snatched away from you almost as quickly just because it doesn't fit with what a so-called "higher species" perceives as the natural order, with nothing you can do about it whatsoever.
Joe's death is even more horrifying than you'd think. If you look closely, he was already wheezing when Fly asked him what happens when a fish drinks too much antidote; but he was still capable of speaking underwater. This means that, at that point he still could technically breathe underwater... but not get enough oxygen from the water. He suffocated slowly, slow enough to realize his mistake and feel his own brain shutting down.
Fridge Logic
How does MacKrill know there's a time limit on using the antidote?
