Manatsu starts attending Aozora Junior High School. She goes with Laura, a mermaid, to look for a new Pretty Cure candidate, but if the students find her she's in big trouble...!

Manatsu and her friends are searching for Laura who was captured, when they come across a cruise ship that was turned into a Zenzen Yaraneeda. Meanwhile, Laura escapes the Witch's Mansion, and finds her friends on the cruise ship. That's when a miracle occurs and Laura transforms into Cure La Mer!