The backstory to this atmospheric, moody psychodrama is the dark side of football culture. The very serious issue of bad off-field behaviour by male players is overlain here with the delicate story of a woman, grieving for the loss of her baby, who fears she may never conceive again.
As a solace and distraction, photojournalist Claire (Laura Gordon) takes herself to the beach, where she captures with her camera images of life and death on the shore. The coast is spectacularly beautiful, but it's clear that all is not well with her.
Although she and husband are close and attend a grieving parents support group, there is some strain in their relationship.
Then suddenly it looks like Dan (Rob Collins from Cleverman) is seeing someone else. There he is, in plain sight as Claire drives past, at the entrance of a Corio Bay motel with a skimpily dressed young blonde.
Is this all the evidence that Claire needs?
Masters of the thriller form Alfred Hitchcock and Roman Polanski would have had a field day with this material, tweaking the dangerous, voyeuristic and confronting elements.
However, writer-director Miranda Nation shows a mature, assured hand with this first feature, relying on the strong central performances from her lead actors rather than ramping up the sensational potential of the film's scenes of drugs, sex and nudity.
Neither Dan nor his good mate since childhood and footie bad boy Brett (Josh Helman) are demonised. They might be. Sporting Pain + Glory tattoos on his pectorals, Helman naturally imports some of the vibe he had in roles in recent Mad Max and X-Men films, but the wild man image is left understated.
Dan told Claire that he was at a fundraiser that afternoon. As he is a football official, this was entirely plausible, but she had spotted him at a motel with another woman.
Later that evening, she doesn't confront him with the lie, but it is soon apparent that she has embarked on an investigation of her own instead.
With telephoto gear in hand, she becomes something of a stalker.
When Claire tracks the woman down, she finds that the focus of her obsession is just a young girl, who declares she is 19, but later admits to being 16.
Angie (Olivia DeJonge) is mouthy and full of attitude and doesn't really mind the attention. Not a talent scout, are you? And she tosses her hair and adopts a more photogenic pose in case the hunch is correct.
Angie confides that she is pregnant to Dan's friend Brett. The teenager's unwanted pregnancy is a cruel irony for Claire who is desperate to become pregnant again.
Her obsession with Angie seems to turn sisterly, looking out for the health of the teenager's unborn baby.
As a relationship develops between them, Claire's actions become more and more bizarre, and Angie, for all her issues seems the stronger. Certainly she is the more interesting.
Undertow is shot in Geelong, the home town of the writer-director on the glorious surf coast of south-west Victoria.
It's understandable that the director may have wished to exploit its natural, untamed beauty.
Images of the city's degrading, old industrial areas are juxtaposed with the windswept cliffs and curling surf.
As it gets harder and harder to distinguish between what is real and what is Claire's subjective reality, the images of water become more dominant. We have drifted a long way from a backstory set in football clubs, locker rooms, drug-fuelled parties and sweaty, sexist bars.
As it gets harder and harder to distinguish between what is real and what is Claire's subjective reality, the images of water become more dominant
Collins is very good as Dan, the sports administrator with a successful career and a designer house and Mercedes to match. But his pastoral actions on behalf of his mate Brett seemed implausible to me. Dan's character, so important to the drama, needed more work at the writing stage.
Despite these reservations, Undertow is in many ways an impressive achievement, and it augurs well for director Nation's next project.
An unusually high proportion of female creatives provided input here, included ace cinematographer Bonnie Elliott, who has made Undertow look outstanding. Female creatives shared the roles of editor, composer and producer as well.