As Pete the Cat searches underwater for a seahorse, he comes into contact with all manner of sea creatures.

Rachel and Kirsty are going to an outdoor adventure camp, but Jack Frost has stolen the seven magical animals from their fairies and they must rush to help Rihanna the Seahorse Fairy save her seahorse, Bubbles, that is somewhere in the camp's lake.

Misty and five fellow mermaids, on a quest to retrieve six magic crystals that will protect the Coral Kingdom for the next year, face a storm sent by the evil Mantora and are driven off-course to the Kelp Forest, where they find a different kind of trouble.

"Of all the creatures in the ocean, sea horses are Echo Reef's favorite. They're sweet and gentle and they glide through the water so gracefully. When Echo discovers that Rocky Ridge, one of her Trident Academy classmates, has his own pet sea horse, she wants one right away. Not everyone agrees sea horses should be pets, however perhaps they are happiest when swimming freely. But Echo thinks that if Rocky can make a sea horse happy, she can too! Can't...

Purrmaid Shelly is taking care of sea horse and new class pet, Bubbles, who looks mysteriously unwell; luckily Shelly and her two best friends discover how to perk Bubbles up, and in the process learn why some animals are not meant to be pets.