In an industry and an art form where the majority of directors are male and most stories are about their needs and dreams, it's almost frightening to come across a character like Fish Tank's Mia. Played by nonprofessional Katie Jarvis, Mia is a bundle of contradictions, full of rage at her former friends but blind tenderness for an abused horse, constantly short-tempered with her younger sister but clearly envious of the girl's simpler view of the world. The narrative of Fish Tank is fairly basic and familiar, but thanks to Jarvis's unflinching rawness and director Andrea Arnold's instinctive handling of Mia's volatile personality, the movie feels almost miraculously fresh despite it.
Living in squalid housing projects in middle-of-nowhere Britain, Mia is spending her summer picking fights with girls who used to be her friends (she tosses in a nasty headbutt), squabbling with her sister (Charlotte Collins) who watches exclusively junk TV, and, when she's sure no one is looking, breaking into an empty apartment to practice her hip-hop dance moves. Mia isn't the most skilled dancer, but it's clear in these moments that it's the only thing for which she feels any passion; the girl unafraid to pick a violent fight suddenly too shy to breakdance in front of anyone.
Two things come to enter Mia's life that have the potential to change it. First she begins a stealth campaign to free a horse chained up in an empty lot, and after the three boys living there nearly rape her when they catch her, she strikes up something of a paradoxical friendship with one of them. He's a roughneck car repairman with not a heart of gold, exactly, but feelings other than malice, which is more than Mia can say for most of the people in her life. Second, and much more importantly to Mia, her mother (Kierston Wareing) brings home a new boyfriend, a gentle and funny Irishman named Connor (Michael Fassbender).
Mia is instantly smitten, though she has no way to show it, while Connor shows her the kind of attention that she's sorely lacked-- encouraging her dancing, laughing at her jokes, even taking her entire family out for a fishing trip. The filmmaking mimics Mia's own sexual attraction to Connor, the camera ogling him and the soundtrack reduced to the sound of his breathing, but his motivations are much fuzzier. Fassbender plays the character's every ambiguous note perfectly, and Arnold shapes the film so strongly around Mia's attraction to him that we catch ourselves from time to time rooting for a hookup that we intellectually know will be disastrous.
A third-act plot twist and a series of terrible decisions on Mia's part take Fish Tank away from the slow-burn character building, but by then we're so invested in Mia and her journey that a slight misstep like that is barely a distraction. What the third act makes irreducibly clear, though, is that Mia is essentially a child-- a child with sexual agency and a yearning to live on her own, but a 15-year-old without the ability to see beyond her own limited, angry world. Mia is a frustrating heroine and often impossible to read, but she's instinctively relatable, in a way few filmmakers would dare to tackle, and even fewer could conquer. Fish Tank isn't a perfect film, but the creation of Mia alone is its own kind of masterpiece.