Continuity mistake: When Triton is turned into a seaweed, the crown has prongs all around it. When Ursula picks it up, the number of prongs has disappeared and the crown is now a diadem.
Continuity mistake: The cake where Ursula comes out-of disappears from the boat's deck between shots.
Continuity mistake: Before Eric is given his statue he sits on a barrel. After he stands up and walks towards the statue the barrel disappears.
Continuity mistake: The right side of the rock where Sebastian places the music sheet is noticeably raised to allow for him to place it there, but swaps to flat in the wide angle.
Continuity mistake: The first time we see Eric's ship the lanterns have a quadrant pattern. In the following shots they swap to three parallel lines.
Continuity mistake: When the chariot with Eric and Ariel jumps over the cliff, they both disappear in the angle shot from below.
Factual error: When Louis the chef starts to sing he mentions typical French things like "Maurice Chevalier", a french actor who became very famous as of the 1920's. Though the movie is timeless, the clothes and lifestyle (pirates, ships, horse carriages) set it long before the 20th and even the 19th century.
Continuity mistake: When Eric's statue is uncovered, the dog crouches next to it and growls. A frame later, the dog stands far away, standing, and totally calm.
Continuity mistake: When the movie begins and the dolphins surround Eric's boat it's completely empty, yet when the angle changes there are sailors everywhere.
Continuity mistake: When the movie starts, Sebastian conducts the orchestra and his baton switches hands between shots.
Continuity mistake: During Eric and Ursula's wedding, the carpet swaps from being plain violet colour when they walk towards the Minister, to having flowers painted on it when Vanessa transforms back into Ursula.
Continuity mistake: The barrels that Sebastian uses for Ariel to float and swim to Eric's boat weren't there in any previous shots, and simply pop-out of nowhere.
Continuity mistake: When Ariel arrives at the dining room, there are just 2 chairs and the table is almost empty. When the angle changes a chair appears together with cutlery, chandeliers and fruit bowls.
Continuity mistake: When Grimsby walks Eric away from the beach, and Ariel sings, the rock where she stands changes from a slim pointy rock, to a squared bulky block between shots.
Continuity mistake: When the storm breaks, in the wide angle showing how a lightning lights the side of the ship, Ariel and Scuttle have disappeared, only to reappear in the following close-up.
Continuity mistake: On the boat, Eric steps by the window where Ariel is peeping, yet when the angle changes he is several meters to the left, where the rope ladder is.
Continuity mistake: While human-Ariel is showing her dress, Eric's dog comes running, Flounder panics and dives in. Thing is, the scenery keeps changing in every single angle.
Continuity mistake: When Ariel takes Flounder out of the porthole, a broken log forming a big crack suddenly appears above him.
Continuity mistake: When Eric's dog comes running on the beach and scares Ariel, Flounder, Scuttle, and Sebastian, all the stuff around them (logs, barrels, iron parts) disappears.
Answer: Yet another Disney urban legend.
Jazetopher