[[quoteright:334:http://static.tvtropes.org/pmwiki/pub/images/h2o_just_add_water_au-show_1098.jpg]]

''H[[subscript:2]]O: Just Add Water'' is an Australian live-action series for preteen-to-teenage girls that has been shown in North America on Nickelodeon and currently shows on TeenNICK as ''[[MarketBasedTitle H2O]]''. The story focuses on three friends who gain magical powers over water and after a trip to the mysterious Mako Island, turn into mermaids following "The Film/{{Splash}} Method" (when they are wet they turn into mermaids, and when they are dry they aren't) after swimming in a [[GreenRocks magical pool]] during a [[WeirdMoon full moon]].

The series was created by Creator/JonathanMShiff. It is mostly about the girls' powers and dealing with them in [[ThisIsReality real life]]. There were initially going to be only two seasons, but due to popular demand a third season was added, with several of the characters missing and a new girl, Bella, added to replace Emma. A {{spinoff}} series, ''Series/MakoMermaidsAnH2OAdventure'', is available on {{Netflix}}.
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!!Tropes related to the series
* AbsenteeActor: No explanation is given for Emma not appearing in "The Gracie Code, Part 1".
* AdultsAreUseless: And clueless and easily distracted, and readily accept some really bizarre excuses with no question.
** Averted with characters like Miss Chatham and Max who have experienced the mermaid problems and offer helpful advice to the girls.
* AllYourPowersCombined: The powers will be divided by those in the moon pool when it's active during the full moon. When Charlotte became a mermaid, she gained all three of the powers because she was the only one in the pool. Bella in the third season also has three powers, as she was alone in her moon pool.
* AlphaBitch: Miriam is ''not'' a nice person.
* AnnoyingYoungerSibling: Cleo's younger sister Kim is a rather extreme case. Elliott, Emma's brother, is an aversion as he is usually nice, friendly and 'squeaky clean' (Rikki's words).
* AsYouKnow: Two minutes into the season 2 premiere Kim reminds her sister that their parents have now split up, for the audience's benefit.
* AwLookTheyReallyDoLoveEachOther: A sisterly version between Cleo and [[AnnoyingYoungerSibling Kim]] occasionally shows up throughout the series.
* TheBeautifulElite: This show is a pretty bad offender of this.
** {{Lampshaded}} in Season 3 when Rikki tells new girl Bella that she only likes Will because "he's the only guy in a five-mile radius not to swoon over her".
* BackForTheFinale: [[spoiler:Lewis.]]
* BaitTheDog: Charlotte spends most of series 2 trying to be nice to people, it's the main characters that are doing nasty things to her. This changes in the last four episodes.
* BareYourMidriff: All the mermaids, in mermaid form and (usually, mostly on the beach) in human form.
* BeautyBrainsAndBrawn: With Cleo as Beauty, although she started off as somewhat HollywoodHomely.
** When Emma leaves in season 3, Cleo eventually went into Brains territory while Bella took over the Beauty spot.
* BirthdayEpisode:
** There was one for Cleo. The one her dad organised for her was embarrassingly childish while the one her friends organized was much more to her liking.
** Later, there was one for Lewis.
* BlackBestFriend: Tiffany, Miriam's friend in Season 1.
* BlondeBrunetteRedhead: Well, blonde, brunette and strawberry blonde. But which one of the blondes is the ''smart'' one? It's Emma.
** In "Red Herring", Emma dyes her hair bright red (a ShoutOut to ''Disney/TheLittleMermaid'').
** When Charlotte becomes a mermaid (but then it would be Blonde Blonde Brunette Redhead or Blonde Brunette Redhead (strawberry blond) Redhead
* BodyHorror: When Emma in a Season 2 episode is poisoned after cutting her finger on a piece of coral, she starts mutating into a white scaled monster.
* BottleEpisode: "The Siren Effect" which takes place almost entirely in Cleo's house, save for two scenes in the Juice Café and one brief shot of Byron on the beach. Also the only episode not to feature a mermaid transformation at all.
** Also "Under The Weather" which happens entirely in Emma's house apart from a brief ending scene in Cleo's room. No costly special effects are used and the one mermaid transformation scene is very brief.
* BraggingThemeTune:
-->''Cause I'm no ordinary girl/I'm from the deep blue underworld...''
* BrattyHalfPint: Kim, Cleo's sister.
* BrotherChuck: Some of the Season 1 characters are no where to be found in Season 2, such as Miriam and Byron. Also Ash in Season 3.
* BroughtDownToNormal: In the Season 1 finale the girls lose their powers for twelve hours after entering the moon pool during an eclipse. And in the Season 2 finale Charlotte tries to get the girls into the moon pool during the fifty year moon in order to make them permanently lose their powers, thinking that she would be the only special girl for Lewis if she did. The other girls manage to overpower her and drop her into the moon pool, causing her to lose her powers forever.
* CallingTheOldManOut: Zane does this to his father, after helping the mermaids escape from Dr. Denman in the Season 1 finale.
* {{Cloudcuckoolander}}: Louise Chatham appears to be one of these.
** Looking at a full moon (or even at just a reflection of one) has the effect of turning the mermaids into this. It wears off at sunrise the next morning, but until then, you can expect [[HilarityEnsues some crazy things to happen]].
* ClingyJealousGirl: Season 2 character Charlotte. Sophie from Season 3 is rather clingy towards her own brother.
* CoconutSuperPowers: We never actually see Emma freezing anything. We see her pointing her hands at an object, a CGI shot of molecules freezing and then it cuts to the object already frozen. While there is an effect to show the girls turning into mermaids, they more often show the girls falling to the floor and being in mermaid form in the next shot, or else diving into the water already transformed.
* ColorCodedCharacters: Not obvious at first but in Season 1 the girls are often coded by the color of their clothing: Rikki (the brawny one, heating power) wears red, Emma (the restrained one, ice power) light blue and Cleo (who gets often caught in the middle) wears purple/pink.
* ControlFreak: Emma, and later Charlotte.
* DoItYourselfThemeTune: Even though the 3rd season reused the OP from the 1st two seasons, this version is sang by Bella's actress, Indiana Evans.
* DoesThisRemindYouOfAnything: The girls waking up after the Full Moon is quite similar to any teen/college student waking up after a particularly boozy night out not having a clue what they might have done.
* EvilRedhead: Charlotte, sort of. And Sophie in Season 3.
* FanService: Season 1 not so much since they were all about 15 but being able to turn into mermaids doesn't stop the girls from walking around in bikinis a lot of the time. And the character of Will who spent the majority of his first episode of the series shirtless.
** FanServicePack: All three girls, as well as Louis in season 2. All the actors were much older so it was okay to have them used for FanService.
* FloatingWater: Cleo's power lets her do this.
** In Season 3, the water from the wall of the cave the moon pool is in combined with the water in the moon pool creates an anti-gravity ball of water.
* FreudianTrio: Rikki is the id, Cleo is the ego, and Emma is the superego.
* GettingCrapPastTheRadar: See KickTheDog below for the specifics but one episode has Cleo left depressed and she swims out into the middle of a known shark breeding ground. Yep, probably the first kids' programme to show a character nearly committing suicide.
* HeelFaceTurn: Charlotte in Season 2. Sophie in Season 3.
* HollywoodNerd: Cleo's boyfriend Lewis.
* HollywoodToneDeaf: Cleo, as demonstrated in "The Siren Effect". The same episode has Rikki doing some truly awful karaoke as well though she's clearly doing it badly on purpose.
* HotScientist: Dr. Denman. The characters even mention she looks more like a Baywatch actress than a scientist.
** In season 3, Cleo becomes one of these.
* HowDoIShotWeb: Each girl spends an episode wondering what her power is. When Rikki tries to find her power the first gesture she makes is the one SpiderMan uses to shoot web.
* AnIcePerson: Emma's powers, reflecting her character.
** This strangely parallels Sailor Mercury's powers changing with the introduction of Sailor Neptune in ''Franchise/SailorMoon'', although with all the {{Shout Out}}s in the show this is perhaps not quite an accident.
* IJustWantToBeNormal: Gracie, one of the three original mermaids felt this way. Louise Chatham also mentions that she also eventually found the burden of being a mermaid too much and gave it up. Mostly averted with the main trio, although Emma and Cleo at first had some trouble adjusting to their new situation, since Emma had to quit the swim team and Cleo hadn't yet learned how to swim and was somewhat afraid of water.
* IJustWantToBeSpecial: When Charlotte learns that her grandmother Gracie was a mermaid, and later discovers that Cleo, Emma and Rikki are mermaids as well, she decides that she wants to become a mermaid herself. She succeeds.
* IdiosyncraticWipes: Splashes of water.
* ImageSong: Bella is fond of these (and the only one of he mermaids to do so), due to singing songs in Season 3.
* {{Irony}}: Becoming a mermaid ended Emma's career as the champion of the school swim team.
* JerkWithAHeartOfGold: Rikki.
* KickTheDog: Charlotte stealing Cleo's locket and making her believe that Lewis no longer cares about her.
* KissingUnderTheInfluence: All three girls kissed their love interests in Season 1 while under the influence of the full moon.
* LettingHerHairDown: The mermaid transformation does this to the girls for no apparent reason. Also Rikki is rarely shown with her hair down at first but wears it down more often as she undergoes CharacterDevelopment.
* LonelyRichKid: Zane.
* LovePotion: In one episode, Nate gets hold of some ambergris which makes him irresistible to the mermaids.
* LoveTriangle: Sort of, between Cleo, Lewis and Charlotte in Season 2.
* MacGuffinLocation: Mako Island often seems to serve this purpose.
* {{Magical Girl}}s
* MakingASplash: Seldom used offensively, though, except as a prank.
* ManipulativeBastard: Charlotte may count as a minor version of this.
* NiceJobBreakingItHero: In one episode, the mermaids and Lewis make a magic potion that can supposedly allow mermaids to grant wishes. However, when it apparently doesn't work, Rikki declares it a waste of time, and she uses her powers on it one more time before leaving. This causes the potion to start growing and it spreads all over the coolroom in the Juicenet café and eventually starts spreading into the café itself. Later in the episode, she also suggests to Emma that she try to use her power to freeze the stuff, which only causes the stuff to spread even faster.
* OurMermaidsAreDifferent. If you look at the picture, you will notice the tailfins being positioned like those of ''whales'', not of ''fish''. Whales, being descended from landborn mammals, have tails after the fashion of human feet, while fish have fins set 90 degrees around it. As the mermaids have scales like fish, they seem like a fish/whale hybrid. Then again...
* OverprotectiveDad: Cleo's, who seems to be afraid that his daughter will get pregnant with triplets if a boy so much as holds her hand. Averted with Emma's father who is nice and normal, and Rikki's is only hostile to Zane because of a misunderstanding.
* ParentalBonus: Emma's behaviour at her first Full Moon is going to make most parents chuckle with how similar it is to a teenager getting drunk for the first time at a family gathering.
* PlayingSick: The girls had to do this in one episode because it was raining outside, however things got a bit out of hand...
* PowerTrio
* PuppyLove: in-universe. One episode had Emma's younger brother Elliot trying to ask Cleo's younger sister Kim out. Kim just took advantage of him and kept bossing him around. He eventually got tired of her attitude and ditched her at the end of the episode.
* PutOnABus: In Season 3, Emma and her family has left town to travel around the world. Later that season [[spoiler:Lewis leaves to go study in America.]]
* ReedRichardsIsUseless: The rare mermaid guide Lewis bought. The girls don't seem interested until Cleo thinks of a way to reunite her parents, and then it's lost while dealing with the wish-granting potion. There's no telling what other information was lost - even a way to only change in seawater, and stay human in freshwater?
* SceneryPorn / RealPlaceBackground: Sponsored by Australia's Gold Coast tourist board and Sea World. Many Americans hadn't really heard of the Gold Coast before this, but wow, is it pretty.
* ScrewTheRulesIHaveSupernaturalPowers: Charlotte entered the moon pool alone. She developed all three of the girls' powers, and turned out to be the most talented at learning them. To put it mildly, this went to her head to the point of nearly killing Nate, and then Cleo's favorite dolphin, Ronnie.
* ShoutOut:
** To various things, one being that Rikki does SpiderMan's MemeticHandGesture when [[HowDoIShotWeb she tries to figure out her water power]].
** The episode "Red Herring" is an allusion to the episode "Rumors" from ''TheSuiteLifeOfZackAndCody'' in which Cody Martin wants to change his look just like Emma and they both end up dyeing their hair red and they both see it and they both end up hating it.
** One of the episodes is called "[[CreedenceClearwaterRevival Bad Moon Rising]]".
* SlapSlapKiss: Rikki and her on-and-off again boyfriend.
* SuperPowerMeltdown: Happens every time there's a full moon to the three girls. Which is often, and quite painful and scary for them.
** Girls and the moon cycle...
* TemptingFate: All three episodes of the second season that features the girls being affected by the full moon has an early scene in which at least one of the girls tells Lewis that they can handle the full moon without his help. All three times, all three girls end up under the moon's influence anyway.
** The girls may be justified in refusing Lewis's help as it is actually his fault (albeit unintentionally as he does make an honest mistake) that the girls end up under the moon's spell in the first instance and it's his attempt to help in the second instance that nearly causes their cover to be blown. Lewis even seems to realize this himself when the third instance comes around as he is happy to stay out of it until Emma calls him in to help after Cleo and Rikki are both already under the moon's spell and the situation is too far out of hand for Emma to handle it given that she is still vulnerable to also falling under the moon's spell herself (which does happen by the time Lewis gets there).
* TheMerch: [=CDs=] and books have become available in Australia; Kate Alexa's made herself famous by the CD. In the US, dolls of the 3 mermaids were available for a short time.
* ThemeTuneCameo: In "Sink or Swim", Emma refers to herself as "Not an ordinary girl."
** In the Season 3 finale, Bella performs the theme song at Rikki's Cafe.
* TheyWouldCutYouUp: Part of the girls' justification for hiding their status as mermaids.
* ThreeAmigos: More BeautyBrainsAndBrawn.
* {{Tomboy}}: Rikki.
* TooDumbToLive: The girls have been warned of the effects of the [[WeirdMoon full moon]]. Yet it - an inanimate hunk of rock - manages to outwit them every single night it's visible (at least for the first season and a half or so; after that, they just become... more immune to it, rather than mastering the art of not looking at it).
** The first moon was unavoidable. #2 was a spot they missed (it ended up reflected as Cleo went to wash her hands after using the toilet).
** The third time also had the moon light reflect of various objects until it was reflected in a glass of water that Rikki was holding. In the first episode of the second season, they didn't realize that the full moon was already out because Lewis had mistakenly come to the conclusion that the moon wouldn't rise for another hour because of a computer program he was using. They usually seem to come under the influence of the full moon due to having missed a spot, or some other unexpected event.
* {{Tsundere}}: Rikki.
* TranquilFury: Rikki lapsed into this when she found out that she was tricked into working for an illegal fish selling operation.
* WalkOnTheWildSideEpisode: Emma gets this twice. The first is a small one where she decides to dye her hair red after being called predictable and the second has her completely slacking off and throwing a WildTeenParty in her house. She's learnt her lesson by the end of the episode of course. Rikki of all people has to calm her down.
* WeirdMoon: Moonlight, when seen through the Moon Pool, turns people into mermaids and grants them powers.
** The effects of a full moon cause the girls' powers to lose control.
** In the final episode, the full moon is overhead at 7:32. The full moon should only be overhead within an hour or so of midnight.
* WhatDidIDoLastNight: The girls usually find themselves wondering this after having been affected by the full moon.
* WhoWearsShortShorts: All the girls though justified since it's Australia.
* WildTeenParty: Emma throws one of these to show she can be fun and it naturally gets out of hand with her mother's crystal ornament getting broken. In another episode Rikki trashes the kitchen with her powers and Emma lies saying they had a party.
* YoureJustJealous: This gets thrown around a couple of times in the episode where the mermaids are infatuated with Nate.
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