Board Thread:Spoilers!/@comment-5094906-20130922174402/@comment-6175354-20130929032218

Charinfox wrote: Then how can she leave, but no one else can? Simple.... Ariel is a mermaid. The rest of the characters are human.

The popular theory, is that mermaids possess the ability to travel between Lands, through the ocean. They prabably also possess some other abilities, such as seducing men. After all, the creators said, they like their mermaids saucy.