Scooby-Doo and the Sea of Atlantis (1990)

After a magic show with Daphne volunteered, they head out at Atlantica in South America, but when the Ghost of Merlin returns, he starts to follow Mystery Inc. on a boat with shipments, and he uses a spinning transformation on Daphne, turning her into Ariel the Little Mermaid, and she heads into the sea remaining in the form forever. And now the gang must find a way to restore her to normal.

Premiered
1990

Characters

 * Scooby-Doo (Don Messick)
 * Shaggy Rogers (Casey Kasem)
 * Fred Jones (Frank Welker)
 * Daphne Blake/Ariel (Heather North/Jodi Benson)
 * Velma Dinkley (B.J. Ward)
 * Merlin's ghost (John Stephenson)
 * 38-Year Old Ariel (Jodi Benson)
 * 40-Year Old Eric (Christopher Daniel Barnes)

Plot
???