Sun’s out, buns out! Kendall Jenner‘s soaking in every last second of summer, showing off her supermodel assets … getting her tan on while vacationing — and, hopefully, she applied sunscreen liberally — ’cause her thong clearly doesn’t provide much protection.

The cheeky model and reality star graced the beach in Ibiza … hitting the water on all manner of aquatic vehicles — boat, jet skis, you name it. If it floats, KJ’s taking it for a ride.

KJ let close pal Fai Khadra drive during the afternoon fun — the one time Jenner covered up just a bit, going safety-conscious in her svelte life jacket.

KJ dropped it low for a few fun photos on the ship’s bow too … laughing while hanging out in the shade of the coastal shelf.

BTW, looks like Kendall’s beach day wasn’t a one-off — ’cause she posted a couple more photos in a different-colored bikini.

Just Kendall and friends in Ibiza this week it looks like … with no whiff of her on-again, off-again flame Bad Bunny.

Remember, the two hit the Mediterranean back in June with Jeff Bezos and Lauren Sanchez … keeping a pretty low profile while grabbing dinner in Greece.

KJ and BB have rekindled their flame in recent months — after initially breaking up late last year, they’ve been traveling together again, though less frequently than when their romance first raged.