A young couple are moored in the shallows off the Gulf of Mexico. Kendra (Louisa Lytton) fishes idly while Betty (Anna Acton) leafs through her book. It sounds romantic, but soon the pair will be dissecting their relationship with clinical precision.

This is the European premiere of Southern American playwright Audrey Cefaly’s 2016 drama The Gulf, which has already opened in the US and Australia. Set in real time entirely in Kendra’s fishing boat, we are privy to circuitous conversations and fractious tensions as the couple while away the time.

Its languid pace is reminiscent of cinematic LGBT+ love story Call Me By Your Name, which also primarily features characters lounging in the sun. Like that film, the fact that the protagonists are gay doesn’t mean their love is idealised or made tragic, as it would be in many other LGBT+ stories. The oppression the pair face for their sexual orientation is only hinted at – the real challenges for their relationship are the buried resentments and insurmountable differences that all couples face. The most appealing thing about Kendra and Betty’s relationship is just how ordinary it is.

Lytton and Acton, who both have a background in TV soaps, disappear into their characters. Lytton’s Kendra is blank-faced and taciturn, occasionally erupting into a molten burst of frustration. Acton’s Betty is the homely Southern girl whose wheedling and inability to stay silent hints at deeper insecurities. Both are well-drawn characters, conjured before us with subtle, surefooted brushstrokes by Cefaly.

The writing itself is almost stately, with every line posing as a possible metaphor yet studiously trying to pretend otherwise. Kendra only ever stays in the shallows when fishing? She’s afraid to risk the deeper waters of a more meaningful, more difficult job and further commitment to Betty. Kendra drops a fun factoid that fish’s hearts can beat up to one minute after they’ve been gutted? We can’t help but think of the pair’s romance slowly sputtering to a halt. Even the play’s beautifully innocuous opening line – “Did you know that Delores Pettaway has 15 cats?” – becomes a leitmotif for loneliness over the course of the drama.

Cefaly treads the line between making the play rich with meaning and overloading every utterance with a deeper significance. Kendra and Acton constantly revisit their earlier conversations. With a writer like Lucy Kirkwood, who uses this trick more sparingly, it mirrors the naturalistic confusion of everyday speech. In The Gulf it makes the dialogue seem overly deliberate.

The plot follows predictable emotional beats, gradually burrowing down into what makes the characters tick. We’re given insights into their hopes, their fears and their pasts. It gives a comprehensive portrait of both women, yet when childhood traumas are wheeled out then the writing loses some of its subtlety and treads familiar ground.

Yet, despite these misgiving, the play for the most part feels completely real. The immersive set – merely a boat, a pier and some trees – both transports us to a faraway place and claustrophobically traps us there when Kendra realises the motor of her boat is broken and the pair are trapped. Having the lights dim by slow degrees so that the audience don’t notice that night has fallen is the icing on the cake as far as the play’s naturalism is concerned.

It’s undeniable that this is sophisticated stuff. It’s no surprise that Cefaly has won several awards, and Matthew Gould’s direction is unassuming and assured. The Gulf is an emotionally intelligent play with a bleak message about our ability to overcome the things that divide us in romantic relationships.

The Gulf is playing at the Tristan Bates Theatre until 5 May

Photo: Rachael Cummings