The reality television star posted a clip to Instagram ... saying she's taking a lesson with Austin Keen -- a world champion skimboarder and wake surfer.

He's in the back in one of the clips KK posted, shredding the gnar as the two hold onto the boat that's chopping up the water and creating waves for them.

Eventually, they have to let go of their hold on the ski rope ... and, when they do, Kim's got her feet stable beneath her -- looking like a total pro out there.

She's not pulling off any fancy tricks yet ... but just keeping her feet under her is quite the accomplishment, and you can see from the look on her face she's proud of her achievement.

Kim's no stranger to water activities ... she's got a small mansion up in Idaho where she goes to get away from it all -- unclear if that's where this video was shot.

Of course, Kim has the beach back in Los Angeles ... though ocean surfing may be a bit too daunting at this point for the mogul.