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.
Continuity mistake: When we first meet Max, his front paws swap from white in the front angle, to grey in the angle shot from behind.
Continuity mistake: The lettuce under which Sebastian later hides, wasn't on the table in the first place.
Continuity mistake: The chef throws flour on the dip where Sebastian is, turning it from brown to half brown-half white. A frame later, the whole mix is white.
Revealing mistake: When Max and Eric first approach Ariel and she is behind a rock, there are no footprints in the sand.
Continuity mistake: The maid brings 3 dishes with the food. Leaves one for Grimsby and walks behind his chair towards Eric. A frame later, she has magically disappeared, yet Eric and Ariel have their plate right in front.
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 Ariel is singing to herself in the bathroom, she swims to a mirror on the wall and plays with her hair and there's no flower next to the mirror on the wall. But in the next shot there's a flower on the wall which she puts in her hair and then gives to her father.
Other mistake: When Ariel is at the dinner table with Eric and Grimsby, Ariel takes Grimsby's pipe and blows it in his face, yet when he wipes his face there isn't any black stuff on his hankie.
Deliberate mistake: When Eric's ship blows up, his statue bobs up and down. A statue this weight would not be able to bob up and down for even a second. It would just sink straight to the bottom.
Continuity mistake: When the crown falls off Triton's head it has eight prongs, instead of the usual five.
Deliberate mistake: While trying to rescue Ariel at the end of the movie, Eric harpoons Ursula's arm, leaving a black cut. But in the following shots of Ursula, the cut is gone. (Due to Disney's practice in not leaving injuries onscreen).
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: 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.
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