The animation is definitely sub-par for Disney. Ariel's head grows and shrinks erratically, from shot to shot. Her hair usually stays the same size (not always), and whenever she pops her head out of water, sometimes it's dripping wet (like when she watches Eric on the ship) and sometimes it's 100% dry (like in meeting Scuttle).
The timing is also off. In the first part of the movie, it switches from night to day, depending on the mood of the scene. Oh, it's daytime when Ariel sings Part of Your World? Guess what, two seconds later, it's nighttime while the humans are on the ship and using fireworks. Ten minutes later, after the drowning scene, Ariel takes Eric directly to shore and it's daytime again, so she can sing a reprise.
The end of the movie is more consistent with what time of day it is, but I think that's only because "Ariel has three days as a human" is a major plot point. Either way, I would demand a refund, because Ariel's three days is more like two and a half days, since she doesn't become human at sunset.
Gah, the end of the movie is kind of frustrating. What happened after Kiss the Girl? Are we seriously supposed to believe that Eric and Ariel rode back to the palace in silence? Like, he tries kissing her once, then seems to completely give up on the idea. THAT IS DUMB. Here is a more realistic version of what happened after the song:
Eric: Oh my gosh, I'm so sorry! I didn't mean for the boat to tip over! Are you okay?
Ariel: (nods and smiles at Eric reassuringly)
Eric: (helping her up) We...we should get back to the castle and dry off.
Ariel: (grabs Eric and makes out with him passionately)
Sebastian: Sweet hot lovin', that should end the spell!
THE END OF THE MOVIE!!!!
Seriously, Ariel has no sense of urgency when it comes to kissing Eric. I know that you can't rush true love, but she could at least do something. There is no reason why Ariel cannot initiate the kiss with Eric. The fact that she doesn't even try is stupid.
Speaking of stupid, I am upset that Sebastian does not tell King Triton about the deal with Ursula, until it is literally too late for him to do anything about it. Sebastian threatens to tell Triton immediately, and then he doesn't because, um...true love or something. Sure, that's a good reason for Sebastian to stay in the human palace where people keep trying to kill him.
Did Ursula-Disguised-As-A-Human really intend to marry Prince Eric? If the wedding hadn't been interrupted, they would have been married before sundown. Just saying.
My girlfriend and I both got confused by Ursula's introduction scene. She was confused as to where Flotsam and Jetsam are during the scene. It seems like they are in Ursula's house, because she talks to them. However, they can't be in her house, because Ursula's magic glass which is connected to their eyes shows what Ariel is doing. So either they were spying on Ariel already, or Ursula doesn't really need their eyes to spy on Ariel.
The thing which confused me was Ursula's throwaway line, about the days before King Triton showed up, when she lived in the palace. What is this? Ursula used to live in the palace, and King Triton dethroned her? Why can't we learn more about that backstory? That seems more interesting than "whiny teenager feels misunderstood by parents".
Also, dang, King Triton is abusive. I bet that's the reason his wife is no longer around.
In a more direct response to the commenter, Ariel could not have used tides to get on and off the shore that quickly. She is so far away from the shore that she would have had to bring Eric there during high tide, then she waited two hours until low tide. Of course, the movie is inconsistent about how far inland they are (the far-off shot has them several feet away, the shot of Eric standing has him two inches away), so I guess there's some wiggle room. Either way, I maintain that there should be marks on the sand somewhere in that scene.