Soho House New York celebrated its 10th anniversary Thursday night with a wet-and-wild rooftop bash featuring a performance by English band Mumford & Sons.

Actress Carey Mulligan — who’s married to Mumford & Sons lead singer Marcus Mumford — J.Crew’s Jenna Lyons, Jennifer Connolly, Paul Bettany and others gathered under a clear night sky around the rooftop pool of the members-only club for the event.

The Brit singers encouraged happy audience members to take a swim as they got deeper into their set list. “I’m not a mathematician, but there are only a few of you in the pool,” banjo player Winston Marshall told the crowd, adding, “Why are there no fat people here?”

On command, many guests jumped in — some fully clothed — including Lyons, who was lofted onto a large inflatable swan and floated across the pool during the performance. While the bottom of her plunging dress was soaked, she kept it on all night.

The audience got a bigger surprise when John Legend hopped onstage for an impromptu performance with the band during their karakoe section.

Mumford & Sons first offered the mike to anyone who knew the words to AC/DC’s song “You Shook Me All Night Long.” A shy fan raised her hand, came to the stage and belted out the rock hit, impressing the crowd.

Next, they asked for a lead singer for Marvin Gaye’s “I Heard It Through the Grapevine.” Legend, who was enjoying the show from the side of the pool, popped up behind the keyboards and belted out the tune alongside Broadway star Alysha Umphress, a friend of Mulligan.

Other guests spotted in the crowd included Victoria’s Secret model Erin Heatherton, Anthony Mackie, Kyle MacLachlan and wife Desiree Gruber, Harley Viera Newton, Michael Avedon, Hannah Bronfman, Griffin Dunne, Morgan Spurlock, Gina Gershon, Will Forte, Alan Cumming and fashion designers Timo Weiland, Thakoon, and Richard Chai.