Fangs & Fins is a H2O: Just Add WaterFan Fiction. It centers around the life of mermaid Rose Collins, a quiet, cynical girl who can not get over the murder of her mother six years prior, after she befriends a group of vampires and the complications that then follow.It's more of an AU fic rather than a crossover, though the series was heavily inspired by LJ Smith's works. Most of the canon characters from H2O: Just Add Water appear in the series, and most of them have maintained the basis of their personality, though their names and backgrounds have significantly changed. The original piece concluded in April of 2011.A sequel was released in June of 2011 and explores the mermaid mythology and tyranny of the vampire world's government that was introduced in the original fic more deeply. It may be read here
Fangs and Fins provides examples of:
Abandon Ship: Both Lily/Lewis and James/Rose were treated to this later on in season 1
Ambiguously Evil: Violet, until the latter half of season 2 took the 'ambiguous' out of it. Same goes for Petra, who seemed to be kind yet misguided throughout season 1 and the first half of season 2, before she is slowly revealed to be a Complete Monster after she blackmails Lily.
Byron, who was a slightly less subtle example, initially appeared to be a friend of Lily's, until it's revealed he's Elliot's minion
Ambiguously Jewish: Several of the Nereids have Jewish surnames, but Léa Abel is probably the best example.
Ambition Is Evil: Played straight in one case (Violet) and ultimately averted in another (Ariadne).
Anti-Hero: Most of the characters in one way or another, but most notably Ben who committed a series of completely unjustifiable murders.
Arranged Marriage: Arianna discovers that her mother and James's father are planning one between James and herself. They are first cousins.
This seems to be very common between the families who have family members on the Council and becomes a major plot point in season 2 when Sofia and Katharina are pitting against each other for Ben's hand.
Ascended Extra: Arianna made a few appearances in the last few chapters leading up to the finale but was promoted to the main cast during the sequel/season two.
Ben was more of a background character until halfway though the story when he was promoted to the main cast. Now he gets more page time than James.
Will - sanguine, Ben - choleric, James - melancholic, and Lewis - phlegmatic.
Freudian Trio: Rose (Id), Lewis (Ego), and Lily (Superego). Also Ben (Id), Lewis (Ego), and James (Superego).
Friend Versus Lover: Subverted. This is what leads Lily to break up with Lewis because she thought their relationship would be weird for Rose or too hard for her to handle.
Generation Xerox: Played with. Aside from the obvious, such as Rose resembling Violet and Ben/James resembling Isaac, Rose and the brothers all possess different personalities than their parents did and Rose is no where near as crazy as Violet was, though if Isaac resembles either brother personality wise he is closer to Ben than James, meaning that Rose/Ben kind of parallels Violet/Isaac, specifically that Violet/Isaac was mostly physical, which Rose almost seems to be trying to convince herself that her connection with Ben is just physical (i.e. what occurred in 2.04...)
Another blatant parallel would be Ariadne/Lea vs. Arianna/Lily. They even do the forehead-touching-thing and link arms constantly. Also - Ariadne/Lea, Arianna/Lily
Season 1: Jewel wants James who is dating Rose who Ben thinks he might have feelings for. Lewis is dating Constance but still isn't over Lily who is interested in both Ash and Byron.
Season 2: James is frustrated that Ben kissed Rose which leads him to question his relationship with both of them, and is a big factor as to why they break up. Ben then feels guilty about possibly pursuing Rose, however James moves on quickly and starts developing feelings for Minerva. Lily thinks she may be interested in Arianna, but she thinks that Arianna may have a thing with Ben, while Lewis pursues Laurel. And James and Arianna get forced into an Arranged Marriage...
Love Martyr: Lewis for Lily, a lot of the time. The guy's devoted, sure, but he does a better job at parenting Rose than Lily does and enjoys the company of Ben/James/Constance. He gets absolutely nothing out of his relationship with Lily, while he got new friends and consistency out of his friendship with Rose - yet he will always take Lily's side if an argument arises.
To be fair though, Rose is insensitive as hell and Lily's side in arguments is generally more logical. Rose wouldn't pick Lily over James/Ben, but Lily sure would pick Rose over Lewis, which he sadly realizes.
Lewis also has an easier time relating to Lily, Rose is very selfish and Lily is very selfless, Lewis can align himself with her because they're personalities are similar. Lily also doesn't seem to take Lewis for granted as Rose often does.
Our Vampires Are Different: For one thing, there are three species of them. The ones who are born - who can digest small portions of human food, drink blood, and have Elemental Powers. The ones who are born but are half-human/half-whatever can do the same. Then the ones who are made - they cannot digest human food, can't have children and don't have any powers.
Parental Favoritism: Subverted. Mr. Wood favors James because he is the only child who is 100% vampire, but the word "favors" should be used loosley...
Minerva's parents have a tendency to favor her older, successful siblings.
Platonic Life Partners: James and Arianna manage to keep things platonic while sleeping in the same bed in 2.02. Despite kissing in 2.03, they both admit to feeling nothing and have spent the rest of season 2 as close friends.
Ben and Arianna. Kind of. Ben definitely had feelings for Arianna prior to finding out she was gay, and his reaction to Arianna and James's Arranged Marriage in 2.03 suggest a repressed attraction.
Rose and Lewis
The direction Lily/Lewis has been heading in as of season 2.
Posthumous Character: Several. Lily and Rose's mother Violet, Ben's mother Anna, James' mother Ashley, and Elliot. However, it is revealed that Violet and Elliot survived.
Ship Tease: Loads between Rose and Ben, but a particularly mean one happens in the first season finale when the two kiss passionately, but are interrupted by Mr. Collins. Rose then goes back to James, inisting that the kiss was a mistake
Oh boy...Lewis/Lily, which is, by far, the most prominent example.
Arianna/James, who even kissed in 2.03
Sibling Rivalry: James and Ben, Lily and Rose. The former is more of a typical rivalry whereas the latter consists more of constant bickering, however.
Minerva with all of her sisters, especially Maire...
Sibling Triangle: Both Wood brothers are interested in Rose.
Sibling Yin-Yang: Lily is logical and overthinks things while Rose is impulsive and sometimes underthinks things. Ben is passionate, mischievous and headstrong while James is serious, thoughtful and cerebral.
Slap-Slap-Kiss: Rose and Ben. They spend the first portion of the original story hating each other, the second half full of UST, and by the sequel things are still weird between them - Rose says Ben is avoiding her, they kiss in Rose's room, etc.
Super Speed: They can move and run much faster than that of a normal human.
Super Reflexes: They can react much faster and quicker to situations than that of a normal human.
Super Strength: They are able to carry or lift heavier objects with much ease and little effort.
Healing Factor: Vampires only. They can get stabbed, shot or wounded and she will heal immediately.
Super Senses: All of their senses, such as sight, smell, taste, touch and hearing have become clearer, stronger and heightened. They are able to see, smell and hear things from a greater distance than that of a normal human.
Triang Relations: Ben/Rose/James was a type 4 in season 1, but eventually morphs into a pretty straight type 9 by season 2.
Lewis/Lily/Rose is a (mostly platonic) type 9, with Lily's loyalty to Rose preventing her from entering a romantic relationship with Lewis.