Continuity mistake: When Ursula and Eric's boat sails away, people suddenly appear on the left side of the boat.
Continuity mistake: When Ariel refuses the eels' help, before they toss the face of the statue, she lowers her head and cries. A frame later the head is tilted to the right.
Continuity mistake: When the song 'Under the sea' begins, Ariel is sitting on a rock. The amount of purple flowers on the sides, specially on the right side, change drastically between shots: They appear, disappear, reappear, change flowers, then to algae.
Continuity mistake: When Ariel first sees the fireworks, they are coming from the boat, but when the angle changes and the boat has moved along, they are being fired from the same spot, though now it's set in the middle of the sea, which is absurd. Some animator screwed it badly.
Continuity mistake: When Sebastian escapes from the dip, the sauce has a white colour. When he throws the bowl over Louis' head it's changed to brown colour.
Continuity mistake: After the shipwreck, when Ariel sings, moss suddenly appears on the rock right below her hands.
Continuity mistake: Eric's ship sails swap from plain to striped when the storm breaks.
Continuity mistake: During the Sebastian and Louis scene in the kitchen, all the stuff on the tables around keeps changing (appearing, disappearing, reappearing) between shots, with no logic whatsoever.
Continuity mistake: When Flounder guides Ariel to the sunken statue of Eric, the statue's visage and position change drastically at least 3 times during the scene.
Continuity mistake: The first time we see Eric's boat, the number of lamps on the stern decreases between shots.
Continuity mistake: When Eric's statue is about to be uncovered, the sailor behind the dog disappears.
Continuity mistake: When Triton lowers his trident to change Ariel into human, Sebastian disappears, only to reappear later on.
Continuity mistake: After Ariel marries, the rope with which Sebastian knocks out the chef suddenly appears.
Continuity mistake: When Ariel marries, all the guests on the boat suddenly disappear.
Continuity mistake: On the boat, when Ariel goes back to being a mermaid and Ursula cries "Too late!", the whole decoration behind (ribbons, laces, bouquets, book stand, etc.) disappear.
Continuity mistake: Between the moment when the dolphins attack Ursula and when Scuttle does, a fallen table and the mess around appear/disappear/reappear between shots.
Continuity mistake: When Eric and Ursula are about to marry they stand inches away from the Minister. When the birds attack her, the ground-level shot shows nothing two meters ahead of them, therefore the Minister and his book stand have disappeared.
Continuity mistake: At the lagoon, when Eric finds out Ariel's name, the oars and the outriggers disappear.
Continuity mistake: The Minister's cape lays sideways first, and straight behind him in the immediate angle.
Answer: Yet another Disney urban legend.
Jazetopher