Emma Gilbert dives into a pool swims a lap, watched by her friend Cleo Setori. Cleo has a stopwatch running, and when Emma touches the side of the pool, Cleo stops the watch and shows Emma the time, which Emma informs her is under her personal best. Cleo tells Emma that she was really motoring during her lap. Emma replies that she will do better than that tomorrow, and that with another two weeks, she will be ready for the regional trials.
Later, Cleo is walking along the harbor at the Runaway Bay Marina when Zane Bennett asks her if she can help him because he is having some trouble with the motor on his inflatable boat. Cleo replies that she is not good with boats. Zane tells her that she will fine saying that all he needs is for her to pass him the tools.
Cleo steps into the boat, and while she searches the toolbox on board, Zane unties the boat from its mooring. He tells Cleo that it took him a while to realize that someone had stolen his spark plug. Cleo finds something inside the toolbox and asks Zane if it is like that, but when she turns around to show him, she realizes that the boat has started drifting away from the harbor. Zane answers with a no and tells her no spark plug, no spark. As his friend Nate joins him on the harbor, he tells Cleo that he was getting sick of that boat anyway. Cleo asks Zane why her, as she didn't steal his spark plug. Zane's only explanation is because she was there, and his dad will buy him another boat anyway. He then says that if Cleo can get it going, she can keep it, but Cleo replies that it isn't funny, to which Zane answers that it works for him.
Cleo yells at Zane as the boat starts to drift out of the harbor, but Zane suggests that Cleo will have to swim for it. As Cleo denies that it is happening, Rikki Chadwick takes a leap off a nearby pier and lands in the boat. Cleo screams at her sudden appearance, then asks Rikki if it is supposed to be a rescue, because it has one fatal flaw without meaning to state the obvious, they are both just floating out to sea. Rikki produces a spark plug that she took, and as she steps towards the motor, she tells Cleo that Zane Bennett is a pig and anything she can do to get under his skin can't be a bad thing. As Rikki fits the spark plug to the motor, Cleo thanks her. Rikki is surprised that Cleo knows her name, and Cleo explains that she had seen Rikki around school since she arrived, and had meant to say hello. Rikki replaces the engine cover, tells Cleo to hold on, then starts the motor and drives the boat back into the harbor. As they pass Zane, Rikki revs the engine up and turns the boat around, sending a large spray of water flying towards him. The two girls chuckle while Zane can only look at Nate.
Rikki and Cleo take the boat for a spin around the waterways of the Gold Coast and wave to another passing boat. As they ride along one canal they see Emma, and Cleo asks her if she wants a ride. Emma replies by asking Rikki if she is licensed, to which Rikki asks Emma if she is her mother. With all three of them aboard, Rikki asks if they want to go out to sea. Emma asks if that is dangerous in a craft their size, but Rikki tells her to chill out as she guns the motor.
Later, the boat runs out of fuel. Emma asks Rikki if she is chilled out yet. Rikki points out that they are floating, not sinking, to which Emma answers not yet. Rikki thinks that they may be out of fuel and asks if they want to paddle to an island that they can see in the distance, which Emma recognizes as Mako Island. Emma suggests that they forget it, and Cleo adds no one goes there, and the island is surrounded by sharks, reefs and mangroves. Rikki answers by telling the other girls that it is all they have, as she produces a couple of paddles. They start paddling towards the island.
Emma pulls the boat up on the island's shore and Cleo asks how they will get home. Emma tells her to ask her friend, but Rikki tells them not to put it on her, leading Emma to sarcastically suggest that it was someone else was at fault for taking the boat a long way offshore. She then produces a mobile phone and tells the other girls that they are lucky that she has it. Cleo explains that Emma is always prepared, to which Rikki answers that she is so happy for her. Emma can't get a signal on the phone and suggests that they should head for higher ground. She and Cleo set off, and Rikki follows them a few seconds later.
As they trek further into the island, Cleo asks Emma if she has any idea where she is going, but all Emma knows is that it's just up. She is still not getting a signal, and Cleo asks her what she will do if she can't get a signal at all, they can't call anyone and nobody finds them, to which Rikki answers that they'll have to draw straws and decide which one of them the others will eat, an idea that Cleo doesn't find funny. It's Rikki's way of trying to relieve the tension, but Cleo says that it is making things worse.
As they continue their climb upwards, they come across a waterfall. Still leading the way, Emma tells the other girls to mind their step. She then jumps across the water and lands on the other side, and Rikki follows her soon after, but Cleo is scared of following them because it is too slippery, and suggests that there has to be another way. She then slips and falls down a path that leads into a cave. Emma and Rikki rush to where Cleo fell in and see where she had landed.
Cleo sits up and tells Emma and Rikki that she is OK, but when they ask her if she can climb up, she tells them that she can't because it's too steep. Emma suggests that she will have to go down and get Cleo, to which Rikki asks if she is crazy. Emma starts the climb down but soon slips and lands close to Cleo in the cave. Emma asks Cleo if she is OK, to which Cleo replies that her leg hurts a little. Emma thinks that it is probably just sprained. Suddenly Rikki also slips and falls into the cave beside Emma and Cleo. Emma asks Rikki what she is doing there, and when Rikki tries to explain that Emma came down, Emma tells her that she was meant to stay up top and throw down a rope or something, to which Emma asks if she is a mind reader, and what rope. Cleo suggests that the three girls should all concentrate on getting out of the cave, an idea to which Rikki agrees.
Night falls as the girls continue their exploration. One of them thinks there is no way out, but Emma finds another passage for the girls to try. Her path brings them to the edge of a pool of water. Taking in the sight, Rikki says "Wow", and on looking up, suggests that it is like the cone of a volcano. Cleo asks if it is going to erupt, but Emma answers that it has been dormant for 20,000 years, so she thinks they are safe. They walk around the edge of the pool, and stooping down, Emma notices some tidal rings, which suggests to her that the pool is connected to the ocean, and may be a way out. She takes off her shoes and dives into the water. Cleo tells Rikki that she is not going to like this.
Later, Cleo calls out to Emma, but Rikki tells her to relax and give Emma a minute. Emma returns to the surface and tells the girls she was right it is approximately a twenty second swim to the reef outside, it is straight through and there is plenty of room for them all to fit. When Cleo looks at where they have to go through, she is scared about the idea, but Rikki points out that there is no other way out, and tells Cleo she can do it, to which Cleo counters that she can't swim. Outside, the light of the full moon is passing close to the cone of the volcano, as Emma tries to reassure Cleo that everything will be fine. Cleo asks Emma how she can be sure, but Rikki tells Cleo to listen to Emma, pointing out that their only alternative is to be stuck down there forever. Rikki stretches a hand out to Cleo, who takes it and allows Rikki to pull her into the pool. At that moment, the full moon appears over the top of the volcano and bathes the girls in its light. Some bubbles appear on the surface of the pool and rise up towards the top of the cone, which leads Cleo to say "Wow", and Emma to remark that it is spooky, before she tells the other girls to concentrate and take a deep breath. Emma goes under first, then Rikki leads Cleo along the passage out. All three of them emerge out in the sea, with Cleo suggesting that it was more than 20 seconds, but she is told to relax, with Rikki saying that she is proud of her, and knew she could do it. They are then bathed in a searchlight as they are found by the water police, who tell them to make their way to the boarding ladder at the rear of the boat. Emma and Rikki swim toward the rescuing vessel, and Cleo soon follows them.
After the sun rises, Emma heads to the beach for a swim, diving under the water and them coming back up. Suddenly, she looks down, sees some bubbles, and seconds later, finds that she has grown a tail where her legs would normally be. Meanwhile, inside her bath, Cleo finds herself similarly transformed, as her little sister Kim knocks on the door and tells Cleo that she cannot stay in there forever. As Rikki goes for a walk, she gets sprayed with water from a nearby sprinkler, and soon finds herself falling over onto the sprinkler's hose, cutting off its supply of water. She looks back and sees that she also now has a tail.
Later, back as their normal selves again, the three girls are together at Cleo's house describing their experiences and wondering what has happened to them. Rikki asks Cleo if there is anyone else there, and Cleo replies that her father is at work and her sister and mother are shopping. Emma asks what happened to them, and Rikki observes that ten seconds after they touch water, they grow a fin. Cleo adds her observation that it vanishes when they are dry, and confirms that it is the same for Emma and Rikki. They all agree about their appearance, but Rikki is the first to describe them as mermaids, a word that leads Emma to tell her that she is not funny because mermaids don't exist, and she finds the idea too weird.
Cleo forgot that her friend Lewis McCartney was coming to help her with biology. He enters and sees Emma and Rikki with Cleo and asks if he got the time wrong. Cleo confirms that they agreed to 9 o'clock as the time, but tells Lewis that something important has come up, but it isn't so important that he needs to know about it, so she has to cancel their appointment. As Lewis prepares to leave, Cleo asks him if he knows anything about mermaids. He answers "No, not really", and Cleo then sees him out before returning to Emma and Rikki. Rikki thinks that Cleo is crazy for asking Lewis what he knew about mermaids, and Emma points out that if anyone finds out about it, they could be in big trouble. She then adds that something very strange has happened to them, but they don't know how, and they certainly don't know why, to which Rikki says that there is a way for them to find out more - to go back in the water, but it is an idea that Cleo doesn't want any part of. On the other hand, Rikki is keen to go, but doesn't want to go alone, so she asks for volunteers.
Later, Emma and Rikki are standing on a rock near the beach, and Emma is not so sure about Rikki's idea, and the fact that Rikki is sure gives Emma no confidence whatsoever. They walk into the beach together, and ten seconds later, they find themselves changed into mermaids again. They spend a little time swimming in the sea among the corals, the fish and a dolphin.
Later, Lewis and Cleo are walking together, and Lewis tells Cleo that mermaids have been around for at least 3,000 years. Cleo asks him if people really believed in that stuff, to which he replies that sometimes they were good omens, but sometimes they brought trouble with them. Cleo asks what kind of trouble, but before Lewis can answer, Zane shows up on a motorbike. Lewis tells Cleo to ignore him, and Cleo suggests that they should go back, but Zane rides along the path straight at Cleo and Lewis, forcing them to split to opposite sides of the path to avoid him. Zane asks them if they were nervous, and Cleo asks him what he wants. Zane tells them that his father didn't appreciate having the water police knock on his door, and Cleo replies that he shouldn't have told her to keep the inflatable boat. Zane says that he doesn't like people making him look bad, especially chicks like Cleo, which prompts Lewis to asks him if he means in front of his dad, adding that Zane sounds like he is scared of his father. Zane asks Lewis if he thinks he is better than him, while Cleo looks at a nearby fire hydrant. Lewis answers that almost everyone is better than him, and he should live with it. As Zane and Lewis walk towards each other, the fire hydrant starts to vibrate. Zane asks Cleo if she has found herself a protector, and taunts that it is not going to do her any good. As he speaks, Cleo stretches a hand out in the direction of the hydrant, and one of the valves begins to unscrew. Zane tells Cleo that one of these days, with or without Lewis, something really bad might happen to her, but at that moment, it is Zane who has something really bad happen to him when the valve comes off the hydrant and sends a huge jet of water spraying on him. The pressure of the water jet is enough to send Zane sliding down a nearby bank and into a stream. When Cleo moves her hand again, the water stops gushing out of the fire hydrant. Cleo leaves a surprised Lewis.
Emma and Rikki return after their ocean swim, with Rikki commenting how after they climb out of the water, everything is back to normal when they're dry, like nothing ever happened. Emma replies that it did, and Rikki says that it is going to change her life. When she asks Emma if there are any words for that, Emma. doesn't think so. Cleo arrives at that moment, telling the other girls to wait while she runs to join them telling them that they will never believe what just happened.
Inside the house, Cleo gets a glass of water and starts to make the water in the glass grow, right in front of Emma and Rikki. Rikki asks Cleo where the extra water is coming from, but Cleo answers that she doesn't know. As she does so, she takes her hand away from the column of water, and it starts to fall towards the other girls. Emma puts her hand up to fend it off, and suddenly, the column turns to ice. After a few seconds of shock, Emma asks if she did that, and Cleo observes that it wasn't her. Rikki remarks that it is over the top and she is getting tingles now. Emma says that all she did was to put her hand up, and as she does the same action, the water in a flower pot freezes. Rikki then tries pointing her hand at the water, but nothing happens. She remarks that it is unfair, and asks why the other girls get to do the cool stuff. Cleo thinks that cool isn't the word, but scary is. She tells the girls that they should have seen the look on Zane's face. Emma counters that it isn't funny, telling the other girls that they have to keep it a secret from everyone, otherwise they could end up dissected or in a circus. Cleo asks if the secret is between the three of them, to which Emma confirms that it is their secret and their responsibility, and no matter what happens, they are in it together. Rikki asks if it means that they are married, a point that Emma says is actually funny.
- Recurring characters introduced: Nate, Zane, Kim and Wilfred.
- Rikki is the only one who doesn't scream when falling down the cavern.
- Cleo's arm was slightly wet after she 'unscrewed' the fire hydrant. But she didn't change into a mermaid.
- All the underwater scenes were filmed at 'Sea World'.
- A time-lapsed video of the beach at sunrise was used to show passage of time.
- The title theme song "No Ordinary Girl" was written by Shelley Rosenberg.
- First version of "No Ordinary Girl" sung by Ellie Henderson and the first opening intro and closing credits sequences.
- Season 1 started filming from October 10th, 2005.
- A book based on this episode is H2O: No Ordinary Girl.
- First episode directed by Colin Budds.
- This is the first episode air in 2006.
- When Rikki tries to discover if she has any power over water, the first gesture she makes is the same one Spider-Man uses to shoot his webs.
- International Airdates:
- Denmark: February 2, 2008 on Jetix
- Poland: September 8, 2007 on Jetix
- Brazil: December 21, 2009 on Rede Record (Brazil Channel)
- This episode first aired in the United States on March 14, 2008 along with "Pool Party" as a TV movie on Nickelodeon.
- Cleo: Emma's always really prepared.
- Rikki: (sarcastically) Oh, I'm so happy for her.
- Rikki: Zane Bennett's a pig. Anything I can do to get under his skin can't be a bad thing, can it?
- Zane: Cleo, hey Cleo. Yes, that Cleo. I'm in some trouble here. Can you help?
- Cleo: Ahh, (shakes head) I don't think so.
- Zane: Come on, please. My Zodiac won't go and all I need you to do is just pass me the tools.
- Cleo: I'm not good with boats.
- Zane: You'll be fine.
- Emma: Whatever happens, we're in this together.
- Rikki: That doesn't mean we're married, does it?
- Emma: Are you licensed?
- Rikki: Are you my mother?
- Emma (After the Zodiac breaks down): Are we chilled out yet?
- Rikki: So, we're floating, it's not like we're sinking.
- Emma: Not yet.
- Zane: Nervous?
- Cleo: What do you want, Zane?
- Zane: My father didn't appreciate having the water police knock on his door.
- Cleo: Well, you shouldn't have told me to keep the Zodiac.
- Zane: I don't like people making me look bad Cleo. Especially chicks like you.
- Lewis: In front of your dad you mean Zane? Sounds like you're scared of him.
- Rikki: About 10 seconds after we touch water we... we grow these...
- Cleo: ...and it vanishes when we're dry. And that's the same with you two right? The tails are like...
- Emma: ...exactly like...
- Rikki: We look like mermaids.
- Emma: Now that was actually funny.
- Rikki Chadwick - Cariba Heine
- Emma Gilbert - Claire Holt
- Cleo Sertori - Phoebe Tonkin
- Lewis McCartney - Angus McLaren
- Zane Bennett - Burgess Abernethy
- Nate - Jamie Timony
- Kim Sertori - Cleo Massey
- Wilfred - Ariu Lang Sio
- Rikki Stunt Double - Nicole Downes