Spanish-born Kat (Natalia Tena) and English Eva (Oona Chaplin) are a gleefully, almost nauseatingly happy couple who live on a funky reconditioned barge on which they chug along the canals of London. Neither has a particularly well-paying job – Kat wants to get deeper into boat-building but pulls pints at a pub, while Eva teaches salsa – but they get by on a steady diet of intense love, tequila and hot sex.

A few key events lead to a realignment of their priorities: their beloved cat Chorizo dies, leaving a big pet-sized hole; Kat’s best friend Roger (David Verdaguer) comes to visit from Barcelona, and Eva starts longing to have a child, particularly so someone else will remember her beloved, kooky hippy mother Germaine (Geraldine Chaplin, Oona’s mother in real life). Kat is less enthusiastic about the baby idea, but goes with the flow when Eva suggests they ask a willing Roger to donate sperm for their home insemination programme.

Although there is a script here, credited to Jules Nurrish and director Carlos Marques-Marcet (his debut before this was 10.000 Km, which also starred Tena and Verdaguer, in that instance as hetero lovers), the dialogue feels utterly spontaneous, free-floating, and the core trio convince completely as well intentioned, smart, funny young people determined to live a little differently from the previous generation.

However, that idealistic goal isn’t as simple as it looks, just like parenthood, of course. But what’s really compelling is how unobtrusively the big-theme stuff gets knitted in. Like a barge trip the pace is unhurried, observant, quietly contemplative. Marques-Marcet loves to hold on his actors as they simply walk down a towpath, or go for a morning run, thoughts flickering wordlessly across the faces like shadows cast by trees or clouds. It’s a thoughtful, honest and touching work, especially for women who love women, and also love canals.