Dianne Bates and her sons Jason and Bret come to the underwater base ORCA for six months. They meet Winston Seth which is Dianne's assistant. Sher is going to study whales. Brett finds the place cool, but Jason donesn't like it. They also meet commander Lucas. At dinner Brett meets his new friends Zoe and Froggy whos real name is Jake Reilly{}. Dianne, Winstorn, Jason and Brett go out with the boat to put a transmitter on the whale. A girl comes up out of the ocean and stops Jason when he is about to shoot the transmitter on the whale, so Dianne has to do it instead. Nobody believes Jason when he tells them about the mermaid.

Vanessa Lane comes to ORCA and ends up in the same class as Jason. Brett, Zoe and Froggy play a trick on Vanessa and she gets back at Brett and leaves him in a broken boat out at sea. A storm comes up, so they can't search for him. He strands on Neri's island and meets Neri, and tells Jason about her when he comes back.

Jason taks driving licene foor the boat and gets out to sunk a net. The whale charle{} gets stuck in the net and Neri tries to save him but gets also stuck. Jason saves her and later she shows them her island. They promise to keep her and the island as a secret.

Vanessa and Jason go out on a mission with the boat but Neri warns Jason that an earthquake is coming, so they return. Commander Lucas gets angry but the earthquake is for real and Damien and Lee get stuck in a room leaking water. Froggy pulls a trick with the computer called HELEN which stands for Hydro Electronic Liaison Entity 3000{} to try to get them out.

Brett's birthday party proves to be a big hit with his friends but Brett is disappointed when he doesn't receive a gift from his father (his parents are divorced). Following a heated argument between Dianne and Commander Lucas over the acquisition of new equipment for Dianne's research, Winston suggests that they should make an effort to be nicer to one another. Talking with Froggy and Zoe about divorce and stepparents, Brett gets the idea that there may be a relationship at work between his mother and Commander Lucas, especially when he sees how nice they are being to each other of late. Brett's belief seems to be validated when he finds himself being given a private tour of the bridge by Commander Lucas, during which he decides to casually mentions some unsettling details about his mother hoping to disinterest the Commander. After saving Jason from a shark while swimming near her island, Neri tells Jason her life story—that which she remembers.