When Cleo, Emma and Rikki get stranded overnight on Mako Island, a magic pool changes the girls' lives forever.

While Emma competes in a sand castle contest, Cleo must babysit a high-maintenance intern and save an injured sea turtle.

The girls discover a mysterious and ancient mermaid statue and want to return it to an underwater wreck, but treasure hunters have other ideas.

Emma and the girls try to save the day when a storm threatens to wash out a yacht-based birthday party.

Zane's father plans a luxury resort on Mako Island, so the girls swim into action to save their beloved retreat from ruin.

An aggressive blue seaweed attacks Emma, reversing her mermaid powers and forcing her friends to come to the rescue.