Nixie and Sirena won't help Lyla try to "zap" Zac's powers, so Lyla decides to do it alone. This misfires when a waitress spills a drink on Lyla and Lyla rushes to hide in the refrigeration room before she transforms into a mermaid! When she can't dry her tail, Nixie and Sirena must save her before she is discovered!

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.

While listening to Sirena sing, Lyla has an idea. If Sirena sings The Enchantment Song to Zac, he will fall under her spell. Everything goes south when David hears the song and falls in love with Nixie.

Against Nixie and Sirena's advice, Lyla goes with Zac to Mako Island. She steals Rita's Moon Ring to open the land entrance on Mako. But when the entrance suddenly closes, Zac and Lyla are trapped inside.

David and Sirena's relationship continues to grow, while Nixie and Lyla are worried she won't want to return to the sea.

After finding a Moon Ring on the sea floor, Zac gives it to Evie. Now, the mermaids must get it back.

After acquiring the Trident, Zac doesn't know how to turn it on.

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

Rita's cat is turned into a human after walking through a bunch of mermaid powders.

Zac leads Lyla to the Trident; they fight for control of it and Lyla is knocked unconscious.

Lyla teaches Zac about mer history and the ocean but Nixie doesn't trust him.

Nixie agrees to help Cam unlock the Trident, but Evie wants to come along.

Cam betrays Nixie after planning to become a merman and rule Mako.

After Cam absorbs moon pool water, he discovers he has power over water, which gets him a place in the trials for the school swim team.

When Erik dives down and touches one of the rock outcrops on Mako reef, he's transported into a sphere of endless water with no way out.

When Sirena sees a video that shows a kayaker being lured by a mermaid's song, she starts to follow David obsessively, and he falls under her spell.

A surprise birthday party is in the works for Evie, who accidentally shrinks herself and falls into an aquarium after trying on Mimmi's mood ring.

Mimmi takes a job at the marine park, where she meets Chris, a young man who is desperate to get into a dolphin training program.

On the night of the full moon, Zac and Ondina sneak away to Mako, and Ondina reveals her plan to destroy the chamber.

At the marine park, Ondina and Mimmi get into trouble when a dolphin splashes them and a little girl sees them transform into mermaids.

When Evie comes down with a fever that causes the temperature in the room to soar, Carly suspects that her friend is keeping a secret from her.

When Erik learns that the trident stone is the missing element needed to activate the merman chamber, Zac gives it to the mermaids for safekeeping.

The chamber's true purpose is revealed: to drain the magic from all mermaids. Zac risks his life to shut it down and restore the mermaids' magic.

Weilan mistakenly makes tea for Rita using a magic growth accelerator. Can the mermaids cure Rita before Mrs. Trumble takes over her principal job?

A priceless artifact recovered by a deep-sea treasure hunter provides a clue as to how the mermaids can defeat the water dragon.