7. Ariel is a hoarding graverobber
We need to talk about Ariel. It's normal to give the youngest child a little leeway, but this is more than just acting out. Ariel is making trips to sunken ships and coming back with a satchel full of trinkets -- items that used to belong to the deceased. Not everyone dies in a shipwreck, but casualties are common enough to the point where plundering a dead vessel is essentially watery graverobbing.
People lived their whole lives on these decks, and many went down with the ship. When Ariel snatches up those plentiful gadgets and gizmos, she's disrespecting the departed. Hell, their disintegrated remains are probably still floating around there somewhere. And that fork that she grabs at the beginning of the movie? Someone ate with that fork, and that someone is probably dead.
Ariel yearns to be a part of the surface world, but she doesn't seem to actually care about the people who live there. Instead, she fetishizes their culture and surrounds herself with physical goods she's stolen from them over time. Imagine a lonely American guy who loves Japan so much that he fills his room with mementos he looted from a graveyard in Tokyo -- that dude is basically Ariel, only less cute and with more neckhair.
You can't blame all of this on ignorance. Ariel is 16, and probably has a good handle on the meaning of life and death. And yet for some reason, she sees no problem with building a shrine to humanity with precious thingamabobs pilfered from the tombs of the same civilization she claims to idolize.
Judging by the vastness of her collection of human whozits and whatsits, Ariel has been taking these creepy souvenirs for a long time. In all likelihood, she's probably run afoul of a human corpse, the bloated remains of someone unable to evacuate the ship before it sank. That should be a transformative learning experience for a young girl, but it's never addressed in the movie; we're left with the impression that if she were still stuck in the sea as a mermaid, she'd continue graverobbing on the regular.
Hell, Ariel would have probably been excited to see Prince Eric's ship sink if she hadn't just fallen for that dreamboat. To someone who scavenges things from sunken vessels, this is what we call a "jackpot."
On top of that, Ariel seems so hellbent on being "part of that world" that she's even willing to sell out her own people.
6. Ariel gladly signs up to eat her friends for the rest of her life
The mermaids of this movie seem to live in a strange equilibrium with nature. All of the local sea creatures appear to be pretty happy with the situation going on in Atlantica, which is why so many different species show up to Ariel's "unveiling" in the opening number. So why would Ariel want to be part of a world that literally eats the old world to live?
Prince Eric and Co. live by the water, and logically eat a lot of seafood -- the French chef's kitchen is chock-full of the stuff. You'd think her first meal with Eric would set off some alarms, but she's totally cool about it. "Sure, this meal looks exactly like Sebastian, the friend that I am currently hiding under a dish cover, but it's not like I'm eating him. It's just another crab who could once walk and talk and also happens to look exactly like Sebastian."
It's not like Ariel doesn't understand the concept. In a line during Under the Sea, one flabby fish laments the possibility of being put on a platter, set for human consumption. Nobody is unaware of the fact that humans dine on sea creatures -- in fact, they find it horrifying. Witnessing the French chef's preparation of fish disgusts Sebastian to the point of vomiting.
Can you really blame him? To anyone who lives in the ocean, gutting a fish is like a real-life Fatality straight out of Mortal Kombat. It's concerning and frankly, a little disturbing that Ariel is capable of eating living beings that look like the bottom half of herself. To her, it's a sacrifice she's willing to make in order to live out her dream of a life on the surface.
Then again, life under the sea can be pretty horrific for those low enough on the food chain. Take these poor clams, for instance:
Along with what seems like the entire ocean, these mirthful mollusks join in on the delightful if puzzling Carribbean anthem that somehow made it to a body of water between the UK and Norway. The clams are seen dancing around and providing backup vocals and uh, also appear to offer themselves up as musical instruments.
That... doesn't seem fun. Humans in general are a pretty terrible species, and even we don't rap our hands on the heads of living creatures just because they make cool steel drum sounds. Not that it makes it much better, but maybe those clams are dead? Atlanticans seem okay with using the husks for Ariel's would-be musical debut at the outset of the movie. And then there's the other major use for clam corpses...
That's right. Ariel's famous bra is made out of clamshells, the remnants of a species which the movie tells us are intelligent and capable of the art of song. In any other universe, wearing a corpse is usually a clear indicator of a serial killer. But hey, nobody is going to argue that she's not totally owning that look.