Kim Kardashian's bringing the wet t-shirt concept to the open ocean ... diving beneath the waves in her tiniest white top -- and, giving fans a look at everything underneath.

The reality TV star turned mogul got really playful during a photo shoot at the beach earlier this week in the Bahamas ... hitting a series of poses on the sand while smoldering for the camera.

She's got a pair of blue bikini bottoms and a white t-shirt on here ... though when the water hits it, it doesn't appear she's wearing a matching bikini top underneath it.

Kim's not facing down anyone in a competition for who is wearing the wet t-shirt better ... but, we gotta say it wouldn't be much of a contest -- 'cause Kim would crush anyone trying to oppose her.

KK's not above a silly shot either ... diving head first into the waves -- and popping up with a huge smile on her face.

Unclear what exactly this shoot is for, although we've seen her posing in the Bahamas this week already in a separate outfit ... of course, Kim's a perpetually busy superstar with a lot of different irons in the fire.

Earlier this month she even got married ... on TV, that is. She filmed a scene for the upcoming Ryan Murphy-created show "All's Fair" where she got married on a beach. It's her second major role after previously appearing on Murphy's "American Horror Story."