H2O: Tillsätt bara vatten

Rikki and Cleo are about to face their final year at school together without Emma, who has gone traveling with her family.

Will is thrilled to see the girls at school and asks for help relocating the Moon Pool.

Bella is pleased and Rikki wary when Cleo applies for a new job as an assistant dolphin trainer at the marine park.

Valentine's Day comes to the Gold Coast, and the girls all seem to be having trouble with love.

Zane's management style is steering the cafe in to debt, and Rikki is not impressed with his new idea to hold a dirt bike race at the cafe to bring in more money.

Bella tries to set up a study date to spend more time with Will.

Cleo and Kim's father Don, takes them to the beach to get to know his new girlfriend.

The girls prepare to sleep over at Cleo's for the full moon, to try and protect themselves from any water attacks.

Lewis tells Cleo not to experiment with the floating water they collected from Mako, but she cannot resist resulting in an interesting day.

Rikki and Cleo warn Bella to stay away from Will when they realize he has made a connection between Bella, Mako, and the full moon.

Sophie is trying to train Will to be a professional free-diver, except he'd rather spend time swimming with Bella.

It's Rikki's birthday and it's going to be an eventful day.

The day of Don and Sam's wedding arrives, and Kim tries to ruin everything.

Cleo finds an unusual crystal in a rock from the Moon Pool.

Bella comes up with an idea to hold a fundraising event for the charity Dolphin Rescue at the café.

Frustrated by the water tentacle's constant attacks on them, Rikki travels to Mako Island at the full moon in order to confront it.

Cleo is introduced to Ryan, a geophysicist working for Sam.

Kim lets slip to geophysicist Ryan that Cleo and the others spend a lot of time on Mako Island.

Will is getting sick of Sophie's pressuring him in to competitive free-diving, but agrees to compete in a competition to set a new depth record.

Zane re-hires Sophie as the new manager, who immediately starts making changes to the café.

Will makes Rikki a necklace, similar to Bella's, using the magnetic crystal found on Mako Island.

Cleo is trying to plan study sessions for the girls' final exams, but Bella and Rikki are more preoccupied with finding out about the tentacle.

The Gold Coast is playing host to a massive beach party, and Bella wants to ask Will if he will go with her.

Cleo's dad gets a second job doing a pirate show at the marine park when Kim demands an expensive holiday.

The girls find a way to simulate a full moon, so that they can finish watching the message the Moon Pool was trying to show them.