Sebastian: That's it. I'm booking meself on a cruise.
Melody: Do I have to do this? Everybody thinks I'm weird.
Ariel: We have to keep Melody away from her. Until Morgana is found Melody can't go in the sea.
Flounder: But Ariel.
Ariel: I'm sorry Flounder, but if Morgana is anything like Ursula, she will never give up. This is the only way. Melody can't know about merpeople or Atlantica or even about you, Daddy.
King Triton: Very well, Ariel, you're right.
Melody: What a totally cool feeling.
Answer: She would only be going through that hole when she's swimming, but since she was walking on land there was no need for it. She could've gotten the boat and brought it to shore another way.