Joe, David's brother has bought a new boat and decides to take it out for a spin. His fish finder locates a dolphin, but that dolphin is actually Nixie.

Zac must find a place to hide the Trident from the Mermaids.

When David sees Evie in the water as a mermaid, it puts Zac and the girls' secret at risk unless they can convince David he's wrong.

When Mimmi loses her moon ring in the Ocean Café's cooler room, it creates havoc for David and his brother's business.

Ondina is tasked with teaching the younger mermaids. A mermaid from China joins the pod. During a full moon ceremony, a terrifying beast emerges.

When marine park workers are sent to investigate the reported sea monster, the mermaids must create a credible explanation to stop further inquiries.

When Evie tries using her new moon ring to magically finish her chores, things quickly get out of control. Joe makes an upsetting announcement.

Zac begs Weilan to teach him an Eastern spell few have mastered, which he hopes to use against the dragon. Joe encounters a water ball.