Continuity mistake: When the crown falls off Triton's head it has eight prongs, instead of the usual five.
Continuity mistake: When Grimsby discovers his crab is gone, little footprints have magically appeared on the table.
Continuity mistake: When Ariel spies the guys on the boat, she is under an arched window. Depending on the angle, the space is made of 3 blocks of wood, or 2. This keeps changing randomly all the time.
Continuity mistake: During the eels scene, when Ariel is crying, the stone she lays on is a single stone laying almost flat on the sand; then swaps to a double stone, and when she sends the eels away it is a single stone though way steeper, standing upright.
Continuity mistake: Eric's statue changes between shots, notice the position of the right fist.
Continuity mistake: In the scene when Ariel saves Eric after the ship has exploded he has boots on yet when Ariel has brought him up onto shore they are off, they couldn't have fallen off since they in that time period men wore boots that have to be taken off to at least to the heal and Ariel is tying to save him so she wouldn't take the time to get them off, and leather tends to tighten up when thoroughly soaked so that is another factor to why they shouldn't have come off this also happens at the end of the film after Ursula has been killed.
Continuity mistake: When Sebastian is arriving at the concert, he gets pulled upside down by his Goldfish. When he flips his shell back over and sits in it again, on his left side he has two legs sticking out... then as he starts moving one of the legs just disappears.
Continuity mistake: In the scene when Vanessa gets covered in starfish, she then is bounced up and down by a seal, the star fish are gone.
Continuity mistake: Ariel's hair is the same in just about every scene except one: when Flotsam and Jetsam come into her treasure trove when she's crying, and convince her to see Ursula. Then, the ends of Ariel's hair (even her bangs) take on the same spiky appearance as the eels' fins.
Continuity mistake: When Ursula's wedding ship sets sail, pink and blue pennants suddenly appear on the pier's columns.
Continuity mistake: When Scuttle watches human-Ariel wearing a sail for a dress, the rope, seaweed and plank in front changes for something else (looks like iron on wood or something).
Continuity mistake: After Scuttle takes the fork to his feathers his feathers are all puffy but then a few frames later they are suddenly back to normal without him doing anything.
Continuity mistake: When Scuttle arrives to the dock to tell Ariel about Ursula's plan, a bunch of flowers laying on the wooden planks behind appear/disappear randomly between shots.
Continuity mistake: When Eric's boat leaves with Ursula in, there are ribbons and a long piece of fabric decorating the side of the boat by the 2 portholes, which disappear in later shots.
Continuity mistake: After Ursula eats the shrimp, when the angle changes the rest of the shrimps in the shell become some sort of white beans.
Continuity mistake: When the storm breaks, the ship's look-out appears/ disappears randomly between shots.
Continuity mistake: When Ariel is peeping on the boat, Max licks her face and you can see that the rope next to the window disappears behind a beam. After Eric sees his statue, the rope is now really long and is laying on the deck, forming a big circle.
Continuity mistake: When the movie starts, the big lamp is lit, yet when Triton arrives to light it with his magic trident, it suddenly appears unlit.
Continuity mistake: When Scuttle peeps on the porthole and discovers Ursula, the design of the porthole changes style between the first and last shot.
Continuity mistake: When Ursula and Eric's boat sails away, people suddenly appear on the left side of the boat.
Answer: Yet another Disney urban legend.
Jazetopher