Schumer, 34, says she and her longtime friends were legitimately in shock when they learned the Oscar winner would be joining them on their yearly girls' getaway – not that they were complaining.
"She's the coolest chick you'll ever meet," the Trainwreck star said Monday night on The Daily Show with Jon Stewart. "She's the best hang, she was like one of the gang."
So just how did the Joy star end up on the uninhibited trip? Schumer solves the mystery.
"Once a year I go away with all my girlfriends from high school," she said. "So we go to the Hamptons and Jennifer and I have become friends. And I was like, 'Oh, we're going on a boat tomorrow, you should come.' It was kind of hypothetical, and she was like, 'I think I'm coming' and I was like 'Oh my God.' "
"I filmed a video of me telling my friends – and they're like nurses and teachers – that Jennifer Lawrence is coming on a boat with us tomorrow. So they're all screaming," she continued.
But it appears the group adapted quickly, as evidenced in the photos of the women hamming it up on the boat, with some friends even boldly flashing a nearby ferry.
The Inside Amy Schumer star also says Lawrence took control during a jet ski excursion, with Schumer recounting that she told her, "I'll drive, I've got this. And she was like, no, Hunger Games."
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The only thing Schumer didn't love about their match made in vacation heaven? Having to pose next to the 24-year-old star.
"In all the pictures we took of us, I look like her coach," she said with a laugh. "I look like I'm telling her to take a knee."