What lurks beneath the surface can be dangerous, as any wild swimmer will tell you. There really is something in the water to worry about. But Wild Swimmers is not a documentary campaigning for clean water; the menace here is not E coli but a centuries-old river-dwelling vampire. It’s written and directed by music journalist turned film-maker Ric Rawlins and, like his 2023 debut Rewilding, it is another shoestring outsider horror set in the West Country, amateurishly acted by non-professionals and rickety in way you will either find charming or a chore.

Valerie Kwok is Deji, a journalism student from Hong Kong who is looking into a spate of mysterious deaths in the River Avon. She tracks down a retired police officer who investigated the death of a teenage girl in 2018 that was officially recorded as a drowning. But something felt off, the copper tells Deji: a witness described the girl seemingly pulled under the water, and the postmortem identified snake bites on her neck. The plot only gets sillier as the body count rises, and Deji is joined in her search for the truth by photographer Kim (Caroline Murray).

Wild Swimmers is a horror without the faintest whiff of a scare. The blood looks like food dye and the daft amphibious antagonist does not seem at all perturbed by sunlight. What does feel unsettling is the Avon itself, filmed with mist rising from its surface at sunrise, mysterious and wild, capable of holding secrets beneath its surface. As a genre, horror often reflects the anxieties of its time, but Wild Swimmers isn’t sharply enough written to reveal an environmental message or hint at hidden terrors. Cult status may beckon though.

• Wild Swimmers is at Create Studios, Swindon, on 18 March, then tours.