They've been enjoying a sun-drenched vacation in hot, humid Puerto Vallarta.
And Scott Disick and Sofia Richie kept each other close while jet skiing off the coastline of the Mexican tourist trap on Monday.
The 34-year-old reality star sat behind his swimsuit-wearing 19-year-old girlfriend and stretched his toned arms around her to grab hold of the handlebars.
The self-styled 'Lord Disick' had been spotted earlier in the day modeling bright pink swimming trunks, but was showing off his legs in a tiny black pair by the time he mounted the jet ski.
Scott had a huge smile on his face when he was photographed splashing his way through the shallows. The jet ski was right behind him, with Sofia nearly shoulder deep in the water nearby.
When Sofia was seen wading in the sea holding life jackets, she'd got on a skimpy two-piece with a scarlet top and summery yellow bottoms.
The model had slicked her blonde hair back into a pristine do, winding it into a bun, and she'd accessorized the look with a massive pair of aviator sunglasses.
Scott and Sofia were seen kissing as they floated about in the sea.
The lovebirds were also seen relaxing in a pool.
At one point, Sofia wrapped her arms around her much older man and seemed to be sharing a passionate kiss with him, his back to the purple-tiled rim of the pool.
Earlier in the day, the daughter of Lionel Richie had been showing off her sculpted beach body in striped bikini bottoms and a canary yellow top.
Sofia posted an Instagram picture on Monday of herself cozying up to her boyfriend as they stood on a stretch of sand near the beach, a couple of palm trees visible in the background.
He'd worn a simple white T-shirt over print shorts, while she'd slipped into a wide-set pair of trousers with a skintight white crop top and crepe pink loafers.
Scott's posted an Instagram Story photo of them in the same outfits, she perched on his lap and leaning in toward his ear as he sits on a chair in front of a standing pair of surfboards.
'Surfs up bruh,' he wrote in blue text near the top of the frame.
Meanwhile, Sofia's Instagram Story has played host to a photo of her legs stretching over Scott's as the pair of them lay on a towel, gazing out over a dazzling view of the Pacific.
The Kardashian barnacle and his latest girlfriend have been an item since at least last month, when social media footage showed them locking lips in a restaurant.
In front of them was a dessert plate with: 'Congratulations Scott and Sophia [sic]' frosted onto it.
Graffiti artist Alec Monopoly, a friend of Scott's, had posted an Instagram Story video of this kiss, which took place in Miami to applause from a waiter.
Scott, who earlier this year was linked to Sofia's fellow 19-year-old Bella Thorne, has three children by his 38-year-old on-off paramour Kourtney Kardashian.
Their son Mason's 2009 birth was immortalized on an episode of Keeping Up With The Kardashians. A little girl called Penelope followed three years later.
Kourtney and Scott's youngest child, a son called Reign, was born in December of 2014, and his parents broke up for the most recent time the following year.