Fish Tank. Starring Katie Jarvis, Michael Fassbender, Kierston Wareing and Rebecca Griffiths. Directed by Andrea Arnold.Rated MA15+ (strong themes, sex scenes and coarse language). 118 mins. “Life’s a bitch” chants the rap singer behind the end credits of ‘Fish Tank’, and for once a closing song captures perfectly the theme and mood of the movie that has gone before.Named Outstanding British Film at this year’s BAFTA Awards and winner of the Jury Prize at Cannes last year, it is a piercing, confronting but ultimately absorbing study of adolescence at the lower end of the socio-economic scale in present-day Britain. Writer-director Andrea Arnold is coolly impartial in her study of a 15-year-old girl dealing with the unforgiving realities of life in a depressing environment where there isn’t a moral compass in sight.The way it is artfully shot (by Robbie Ryan) and edited (by Nicholas Chaudeurge) lulls you into thinking you are watching a documentary. There is no “acting” artifice anywhere to be seen. Katie Jarvis, who plays the pivotal role of Mia, has never been in front of a camera before, and was “discovered” by Arnold having a fight with a boyfriend on a railway station — just about an ideal preparation for portraying this character..Mia is a school dropout for whom life is mainly conducting screaming matches with her slatternly mother (Kierston Wareing) and younger sister (Rebecca Griffiths). In the first few minutes of the film Mia lets fly with all the choice four-letter words and implants a Liverpool kiss (head-butt) on a girl because she doesn’t like the way she dances. Jane Austen it ain’t.Dancing means everything to Mia. She locks herself away to play her music and practise her moves (not Royal Ballet terpsichore, you understand — street dancing). When her mum’s latest boyfriend, the surprisingly couth and charming Connor (Michael Fassbender), compliments her on her dancing, her response suggests that this is the first time anyone has given her any encouragement and praise. Not susprisingly, perhaps, she is drawn to him.Connor also provides a video camera so Mia can make an audition tape and apply for a job as a dancer she has seen advertised. In Hollywood tradition, this would signal the girl’s redemption through dance. But this is not Tinseltown; it is a high-rise council estate in Essex where fairytale endings are thin on the ground.In fact, everything points alarmingly to a terrible, tragic ending when Mia realises Connor’s duplicity and strikes out blindly for revenge. It leads to a grippingly dread sequence at Tilbury on the Thames estuary that had me holding my breath and praying it wouldn’t turn out the way it was heading.The film is not for the faint-hearted and there are no easy solutions to the problems it depicts. The fish tank of the title is, one supposes, a metaphor for the way Mia feels helplessly confined in an environment where she just goes around and around with no chance of escape. But a faint glimmer of hope at the end offers at least a modicum of relief from the bleakness of her existence.This BBC Films production is in the proud tradition of BBC docu-dramas that goes back to Cathy Come Home, the famous 1966 TV film about poverty and homelessness directed by Ken Loach. The performances are striking. Katie Jarvis as Mia maintains the expressionless look of the truculent teen remarkably well, and Michael Fassbender’s Connor is a beautifully judged characterisation of the attractive but black-hearted cad. Kierston Wareing and Rebecca Griffiths, as Mia’s family, are so convincing that it is hard to believe they are actors.Transmission Films Out May 27 Mr Jim Murphy is an associate of the Australian Catholic Office for Film & Broadcasting.