No Fringe is complete without a selkie or two. The mythical seal-creatures from the Northern Isles have entranced storytellers for centuries past – and continue to beguile audiences in the present day. Most shows you’ll see, though, are riffs on a single legend, of a man who captures a selkie and makes her his wife. So it’s invigorating to see this new take from playwright Madeline Farnhill, which both tells a brand-new story and moves the action south to the Clyde.

Ciaran and Finlay crew the CalMac ferry between Rothsay and the mainland; it’s a quiet night, and they have plenty of time to chat, reflect and study the waves. The Gaelic-speaking Finlay is happy with his lot, but Ciaran dreams of escaping this “nothing in a sea of nothing” for a new life in Glasgow. The mood turns quieter as, in a searingly emotive scene, the two men remember a colleague who’s been lost. Then Finlay, through his binoculars, spots something in the waves…

The strength of The Selkie is that it’s set, not generically in Scotland, but specifically in the narrow space between Wemyss Bay and Bute. If you’ve ever taken the road west from Glasgow, you’ll recognise exactly where you are; if you haven’t, Ciaran and Finlay’s musings will quickly fill you in. And while it’s odd that sea-creatures from Orkney turn out to speak Gaelic, the clever use of language does cement the concept of a distinct culture beneath the waves, which land-dwellers with a particular heritage can connect with – if they choose.

Sean Russell and Hugo Shack deliver convincing, committed performances as Finlay and Ciaran, adroitly balancing tension and humour as the story progresses and secrets are revealed. Eilidh Park, meanwhile, is mesmerising as the selkie: a woman in form but not quite human in manner, she’s alternately playful and menacing. The direction makes fine use of the tiny venue and with the lights kept low, it’s easy to imagine you are there on the boat, surrounded by the sea and the night.

At just 40 minutes, this is a short piece of theatre, and – looking back on it afterwards – there were times when some more of the story could have been told. In the moment, though, it’s a tale as seductive as a selkie itself, modern yet ancient and anchored firmly in a place and time. With three compelling performances and stand-out writing, it proves above all that there’s space for local stories in this increasingly international Fringe.