The Mermaids are teenage mermaids with valley girl accents. They first appear in Welcome to the Bikini Bottom Triangle. When SpongeBob, Gary, Squidward, and Patrick's stuff is missing, they head to the Bikini Bottom Triangle and see Mr. Krabs with a masseuse. While on the island, SpongeBob and Patrick come across five mermaids. It shows the Mermaids sing which causes the stuff to come on their island. When they sing their song backward, the stuff on the island is returned to its owner. They also want to go to the mall after Pearl informs them of it.
- In the cover of Legends of Bikini Bottom, SpongeBob is stuck in the main drain, Old Man Jenkins is hiding in the sand, Gary is on a parachute, and the Mermaids are cheering for SpongeBob for saving them, but Madame Hagfish helps Ma Angler to capture the Mermaids.
- It is seen that Patrick has a crush on them.