Meanwhile, Ken has taken an internship at a marine biology institute, and has arranged for Barbie and her sisters to stay in a beachside cabin nearby.

Once the group leaves, the 'animal' appears and reveals itself as the mermaid, who magically turns her tail to legs and tries to free the dolphin herself; however, Marlo has locked the gate.

The mermaid introduces herself as Isla, and reluctantly agrees to trust Barbie and return next afternoon when the Vet is supposed to be there.

Meanwhile, Stacie, Chelsea, and Skipper see a sideshow company's helicopter land at the institute, and when they follow it they learn that Marlo intends to sell Emerald to the owner.

Barbie disguises herself as a mermaid and swims the other way, allowing Marlo to pursue and capture her while the rest make it to safety.

Later, once the area is safe, Barbie uses the shell to summon Isla back to the beach, while the dolphins play offshore.