Here is a shark attack movie with a period twist: it is set in 1946, and the reason the characters are intent on diving a section of river patrolled by an aggressive bull shark is that a van full of gold bullion lies at the bottom. This results in an unusual and not unpleasant mixture of aesthetics: gangsters in sharp suits and wide-brimmed hats and a ragtag band of salvage divers whom they hire to recover their ill-gotten gains.

The film also makes good use of its Australian setting, with attractive riverside locations which are again not typical in a shark movie. Hang on, you might think, what’s a shark doing in a river? But don’t worry, they’ve done their homework: this hungry fish is a bull shark, one of the most dangerous and aggressive sharks, and also one that is equally at home in fresh and salt water. (One of the most famous real-life shark attacks of all, at Matawan Creek in 1916, was over a mile upriver from the ocean.) So there’s a new nightmare, just when you thought it was safe to go back to the riverbank.

Unfortunately where the film falls down is its human characters, who struggle to really come alive – and the galling thing is, it’s not for want of trying. This isn’t one of those monster movies where you don’t really need the humans to be memorable because they’re interchangeable fodder for shark attack sequences; this film is trying hard to make you care about the human element. In many ways, the shark storyline takes a backseat to plucky Clara (Hermione Corfield), taciturn Jacob (Jimmy Barriakada) and hard-drinking Ernie (Arthur Angel), whose travails as a diving company are the human interest story. But they’re not all that interesting, meaning you end up waiting around for the next shark attack. It’s a shame, because the idea of making a classy, character-driven shark movie is a fantastic one – it just lacks the vital charisma necessary to really reel us in.