It's a full moon and the mermaids think that if they keep Zac out of the moonlight, he'll lose his powers and return to his land-dwelling self. Then they can return to their pod.
Zac's struggle with his merman secret intensifies when his girlfriend, Evie, throws him a pool party. At the party, Cam pushes Zac into the pool and the mermaids see his transformed state.
Joe, who delivers seafood to the Ocean Café, has a new boat and takes his brother DAVID out for a spin. His fish-finder locates a dolphin, but it's not like any dolphin he's seen before.
The girls sit their final school exams and have to avoid a water attack in public when the full moon rises early.
The girls discover the Mako crystals contain immense energy and need to mount a rescue mission when Zane jealously steals one in an effort to gain Rikki's attention.
Zane installs Sophie as head of staff at the cafe. Bella develops a sneezing allergy that also accidentally triggers her powers.
Will competes in the Free-Diving Championships but afterward chooses to break from the sport and shrug off Sophie's influence on his life.
Christian's sentencing hearing has been set and, believing that he's headed for juvenile detention, Christian decides to stop playing by other people's rules and goes back to his old neighbourhood.
It's a month since Tara's injury and her plaster is due to come off but Tara seems much more focused on her new boyfriend, Christian, and organising the school formal. Sammy and Abigail decide take their relationship to the next level.
Jana's uneasy relationship with Imara is tested on a mission to find a dangerous wolfblood.
An emergency from the wild pack forces Jana into an impossible position.
Kuru reports diplomatically to Omar about Alex's slow progress and Devi to Vashan that she's still a magically clumsy brat living a commoner's life, the rival prince allows her to return as butterfly and seduce Kuru as Juliet, so he'll cease being her only good influence.
ZOEY is sick of waiting and decides to take charge of finding a way home. Back at the cane field, ZOEY and AMBER test out the energy field one more time.
Rikki fears Ryan's explorations on Mako Island will uncover their secrets but Cleo and Bella discount her concern.
Cleo's introduced to Ryan, a young geophysicist who's working for Samantha. Rikki doesn't react well to Cleo consulting Ryan about the Mako rock and a fracture begins to appear in the trio.
Rikki's frustrated by the water attacks and goes to Mako Island on a full moon to confront the strange force in the Moon Pool.
Sophie uses Bella's idea for a fundraising concert and presents it as her own to Rikki to gain publicity for the cafe.
Christian's sentencing hearing has been set and, believing that he's headed for juvenile detention, Christian decides to stop playing by other people's rules and goes back to his old neighbourhood.
It's a month since Tara's injury and her plaster is due to come off but Tara seems much more focused on her new boyfriend, Christian, and organising the school formal. Sammy and Abigail decide take their relationship to the next level.
Jana's uneasy relationship with Imara is tested on a mission to find a dangerous wolfblood.