Kourtney Kardashian and Travis Barker Snuggle Up on Beach Dates

Travis Barker's using Kourtney Kardashian as his sunblock ... snuggling up with his GF for some serious PDA in the sand.

Kourtney and Travis have been hitting up a beautiful section of Laguna Beach the past 2 days, and they've been all over each other ... literally.

As you can see, Kourtney was rocking a bikini top and shorts as she laid on top of the shirtless Blink-182 drummer. Y'know where that leads ... lots of hugging, holding hands and rubbing noses. He also makes sure to get a handful of booty. It's like UV rays and chill.

The lovebirds first ventured down to the sand of Laguna's famous Treasure Island beach Sunday afternoon, seemingly as part of Kourtney's 42nd birthday celebration.

As we reported ... Travis showed off his romantic side with an intricate piece of hanging art hovering over a huge flower arrangement to start off Kourtney's big day, and it looks like they kept the party going down on the shore.

They're clearly loving the location, they were back on the same beach Monday afternoon and snuggling up for more beach action. Hey, if it ain't broke ...