It tells the story of two friends, Claire Brown (Emma Roberts) and Hailey Rogers (Joanna "JoJo" Levesque) who are due to be separated in five days when Hailey moves to Australia. After a violent storm, they discover a mermaid named Aquamarine (Sara Paxton) in the swimming pool of their beach club. The mermaid tells them that she came to find love, which she has heard of but never experienced. Furthermore, she made a deal with her father that if she cannot prove love exists in three days, then she will have to return to enter an arranged marriage. She notices handsome lifeguard Raymond (Jake McDorman), also desired by the girls, and promises them that if they help her win his heart, then she will grant them one wish.
The girls immediately agree, seeing the promised wish as their opportunity to avoid being separated. But can they find proof of love in time?
And as if they didn't have enough problems already, Claire and Hailey's Rich Bitch rival Cecilia Banks (Arielle Kebbel) is growing increasingly suspicious this "fishy" girl and intends to find out what her secret is.
This movie contains examples of:
- Adaptational Nice Guy: Aquamarine is something of a brat in the book, but in the movie shes much more kinder and appreciative from the get-go. She even demonstrates a Big Sister Instinct towards Claire and Hailey.
- Alpha Bitch: Cecilia.
- Arbitrary Skepticism: "You believe in genies?!" This line is delivered by a mermaid.
- Armor-Piercing Question: Aquamarine asks Hailey and Claire why would they still risk their lives for her while endangering their lives in a storm, which leads to...
- Armor-Piercing Response: Hailey and Claire give one to Aquamarine as they risk their lives for her during a storm her father made, leading to Tears of Joy.Claire: We love you, Aqua!
Aquamarine: (smiling) I didn't know you make these when you're happy too!
- Arranged Marriage: Aquamarine is escaping from one because she wants to Marry for Love.
- Beta Bitch: Marjorie. She's Cecilia's chief henchwoman and the taunts the girls more than any of the other minions. She remains in this role until she betrays Cecilia, and leaves her at the water tower and later thinking she's crazy when she tells them about the mermaids.
- Big "NO!": When Hailey and Claire find out Aquamarine wants to find love with Raymond.
- The Boo Radley: Leonard
- Cassandra Truth: Cecilia when she starts trying to tell people that Aquamarine is a mermaid.
- Chick Flick
- Canon Foreigner: Cecilia and her Girl Posse do not appear in the book.
- Disappeared Dad: Hailey's father ran out on the family for his extramarital mistress before the events of the film began. Such being the big reason why Haley's mother wants to move them to Australia, despite Hailey's refusal. Hailey even uses this tragic example to explain "the truth about love" to Aquamarine after she finds her crying.Hailey: Let me tell you something. My dad said he loved me. He said he loved my mother and then he left us! He left us for some other woman! But I guess that's just the way it is, and love doesn't always work!
- "Do It Yourself" Theme Tune: Sort of - Sara Paxton's voice is incorporated into David Hirschfelder's score.
- Mr. Fanservice: Raymond.
- Even the Guys Want Him: Raymond.Claire: She's right. I mean, all the girls are after him. Even a few boys.
- Exact Words: Aquamarine did say that she had to prove to her father that "love" exists. Now whoever said it had to be a romantic love?Claire: What happened to the storm?Aquamarine: You just proved to my dad that love exists.
- Everyone Loves Blondes: Raymond is a rare male example. Aquamarine is also blonde.
- Fourth Date Marriage: Aquamarine hopes that Raymond will have fallen in love with her after three days. He doesn't.
- Freudian Trio: Claire = superego, Hailey = ego, Aquamarine = id
- Girl Posse: Cecilia's friends.
- Godiva Hair: Aquamarine, anytime she is in mermaid form.
- Going Commando: Aquamarine, shortly after her first use of legs and a modesty t-shirt (which is big enough on her to be a dress), it's specifially mentioned she still needed undies (and shoes)
- Gosh Dang It to Heck!/Unusual Euphemism: Aquamarine's form of swearing:Bullshark!
Why that—! That Barnacle!
Crabs! They found me!
- Heartbreak and Ice Cream: Aquamarine eats ice cream in the bath when it looks like it's not going to work out with Raymond. It also doubles as Freeze-Frame Bonus because the flavor is phish food by Ben & Jerrys.
- Heterosexual Life-Partners: Claire and Hailey, and later Aquamarine.
- In Name Only: The plot developments between the book and movie differ greatly: The book's narrative implies it takes place on the Northeast Seaboard, and Claire, not Hailey, is moving to Florida to live with her grandparents (as her parents are deceased as in the movie). Aside from the main four, all of the characters in the movie including Alpha Bitch Cecelia are completely absent. The plot revolves around the conflict between Aquamarine wanting to meet Raymond and Hailey and Claire trying to return her to sea before she succumbs to the elements and the Capri Bleach Club is closed and demolished. Also, the movie treats mermaids differently from the book: Aquamarine cannot transform at all; Hailey and Claire move her around on a wheelchair for her date with Raymond inside the beach club's abandoned cafeteria, but she's otherwise confined to the swimming pool.
- Interspecies Romance: Between Aquamarine, a mermaid, and Raymond, a human. It doesn't work out, but they're okay with that.
- It's All About Me: Cecilia.
- Karma Houdini: Cecilia's ultimate punishment is "getting her driving privileges revoked" by her father. Yeah, even though in a few years she'll be old enough to get her own car and not follow her parents' rules, so it's really a rather pointless punishment.
- She still has to follow those rules for now, though, and has to walk to school, which she doesn't find appealing.
- Averted in a deleted scene: Cecilia, still angry that Raymond chose Aquamarine over her, kicks a bucket full of fish. However, she slips on water and lands into the fish, much to her horror and disgust. She then whines about how she wants her car back.
- Makeover Montage: Part of a shopping trip.
- Nice Guy: Raymond, who is aware of Hailey and Claire's crushes on him as well as aware of numerous girls and boys crushing on him and respects them all nonetheless. He reciprocates the crushes of Hailey, Claire, Cecilia and Aquamarine without using them selfishly.
- One-Word Title: Only One Name-type Protagonist Title. Presumably also because mermaid protagonist.
- Only Friend: Hailey and Claire to each other before they meet Aquamarine.
- Our Mermaids Are Different:
- The movie uses the Splash method of wet = tail and dry = legs. However she must change back into her mermaid form at sunset.
- The movie also gives merfolk the ability to grant wishes.
- The book treats it in a vastly different manner: Aquamarine cannot change at all. Hailey and Claire have to use a wheelchair to move her around on land.
- The Power of Friendship/The Power of Love: Ultimately what saves Aquamarine, Hailey and Claire.
- Rule of Three: Aquamarine has three days to find love, or her father will send storms and tidal waves to force her to come home.
- Shout-Out: The tiles along the swimming pool Aquamarine finds herself in closely mimic the pattern forming the page borders in the original book.
- Supporting Protagonist: Multiple:
- Swiss Army Tears
- Third-Option Love Interest: Both Hailey and Claire were already crushing on Raymond when Aquamarine arrives and she falls for him. Raymond becomes interested in Aquamarine too but also respects Hailey and Claire's crushes on him. Giving them both kisses on the cheek.
- Why Did It Have to Be Snakes?: Claire is terrified of the water because her parents drowned.
- You Gotta Have Blue Hair: Aquamarine has blue streaks in her hair and later so does Hailey who gets it in imitation of Aquamarine.