Coasting, Old Vic Studio, Bristol

Fruit machines in the amusement arcade flare and bleep, waves crash over the shingle and a dead body lies on the beach. This is the twilight world of Natalie McGrath's Coasting, the first full-length play to come out of Bristol Old Vic's new-work programme, Ferment.

Pearl and Ocean live on the edge of respectable society: they flirt with criminality, they loiter under the pier at night and hide from Falcon, the chief of police. But then they spot the body on the beach and Ocean gets involved with a gangster. In the hands of director Emily Watson-Howes, it has moments of real power. But those moments are scattered through an evening that feels self-consciously showy and ultimately frustrates.

The friendship between Pearl and Ocean should be the heart of this play, but it is difficult to care about the fate of characters about whom you can glean so little. The fault doesn't lie with the three performances: Nadia Giscir as Pearl is a vision of corrupted innocence; Tom Wainwright is engaging as a lost young man wandering unwittingly into danger and Falcon, the exhausted chief of police, is played by a wry Helena Lymbery.

The problem lies in the fact that McGrath gives Pearl and Ocean their own language, which combines polari (gay slang) with their own patois. Her writing is highly poetic: Pearl's first line is "shake out the shiver of these cold white bones". But such poetry feels out of place in a production that otherwise attempts to provide a realistic snapshot of a run-down British seaside town in the 1980s.

In short, McGrath gluts herself on language and loses sight of her audience, a point she perhaps recognises when the chief of police tells Pearl to stop her "linguistic jerking off". Thank goodness, then, for Katie Sykes's design. From the tacky fruit machines and garish lights to Pearl's leather jacket and Falcon's dour police uniform, this play transports you to the 80s. Mike Beer's sound design plays no small part, with 80s pop and the screech of seagulls as Pearl and Ocean play on the beach.

McGrath has written a powerful work – but the text feels too cumbersome for performance. The actors sound awkward as they try to fit their characters into the lines they're given. There is a powerful story in Coasting – it just can't get out for all the words.

To 15 October (0117 987 7877)