Continuity mistake: When Sebastian is hiding from the chef under a lettuce leaf in the kitchen, at first he is behind a bunch of stuff on the table. In the next shot, all the stuff is gone, and he's alone on the table.
Revealing mistake: When we first see Max, his paws are leaning on a balustrade and become transparent. Though it may seem like it's an optical effect because they're in the shadows, the next angle shows them fully lit and opaque.
Continuity mistake: After becoming human, Ariel swims and rest on a floating rock amidst the sea. A frame later she is laying on a rocky wall by the shore.
Continuity mistake: When Ariel is swimming back home from her treasure collecting trip at the sunken ship, she has her pink bag. Then the eels' eyes merge from watching her to Ursula's bubble globe thing Ariel doesn't have it anymore. Then when the scene switches back, she has it again. (00:10:45)
Continuity mistake: When Flounder swims through an anchor at the start the anchor has round edges, but when the shark bursts in the anchor has flat edges.
Continuity mistake: The bookmarks in the Minister's bible keep changing colour between shots.
Continuity mistake: The bowl in which the chef dips Sebastian swaps from grey coloured to blue.
Continuity mistake: When Ariel and Eric kiss during the wedding ceremony, the wedding barque is thronged with people, but when Louis the cook chases Sebastian, the deck is suddenly bare of any and every person, including the happily married couple. Quite a flash-wedding.
Continuity mistake: When Ariel is at dinner with Eric and Grimsby, her fingernails are painted pink when she picks up the fork in the close-up, but are not painted when she combs her hair.
Continuity mistake: When Eric first washes up on the beach and Ariel is singing to him, she looks to her left when she hears Max barking, but Max and Grim are actually coming from her right.
Continuity mistake: In the first scene involving Ursula, the shrimp don't appear in her opened case until she reaches down for one.
Factual error: At the end of the film, when Ursula has Triton's powers, she creates an enormous whirlpool that pulls wrecked ships off the ocean's floor. Prince Eric boards one of the ships that is being swept along with the whirlpool's currents, then turns the rudder hard to steer the ship into Ursula. Not possible - in order for the rudder to change the course of a ship the vessel must be moving faster than the current.
Factual error: After Ariel is changed into a human, she swims frantically to the surface for air, and when she comes up she does the magnificent throwing her head back and splashing water everywhere - we've all seen it. But this would mean she would have to actually tilt her head further down in the water before breaking the surface, so she could then throw it back- something that makes no sense for a person who's about to drown, and wants air as soon as possible. Can't have been a "hair in face" problem - her hair was streaming out behind her underwater, so wouldn't have been in the way if she'd broken the surface face first.
Continuity mistake: When Grimsby is presenting the statue of Eric, the huge ribbon around it disappears between shots.
Continuity mistake: When Ariel is at dinner with Eric and Grimsby, she begins to brush her hair with a fork. The prong number of the fork changes from shot to shot. Sometimes three, sometimes four.
Factual error: When Louis the cook chases Sebastian in the kitchen, Sebastian hides in a cabinet full with plates and bowls which reflect the rabid cook's image. However, in both real and mirror-reversed image, his actual right arm (with the mallet) is raised up high. (00:54:15)
Continuity mistake: When Ariel is crying and Sebastian comes to comfort her, there's a vase, two planks and a small bottle behind her. When the angle changes, every object is different, even the area looks much wider.
Audio problem: When Eric and Ariel swim to each other, she says, "Eric, you've got to get away from here." He replies, "No, I won't leave you," but his lips don't move. (Regardless of the reason, still a mistake.)
Continuity mistake: When Ariel and Flounder are going into the shipwreck at the start, Ariel goes through the porthole and Flounder follows. In the frame where he gets stuck, his front fins are trapped firmly outside the porthole but in the next shot inside the boat, they appear inside instead of outside.
Continuity mistake: When Ursula turns King Triton into a seaweed thing, his crown is a normal crown design. When Ursula then picks it up it has turned into a tiara and stays like that for the rest of the film.
Chosen answer: They are all throughout the film but the biggest one is when Eric is steering the ship to stab or skewer Ursula.
Disney-Freak