Ivanka Trump is having some fun in the sun in Costa Rica, enjoying some quality time with her kids at the beach and surfing her butt off in the ocean.

Speaking of Ivanka's rear end, President Donald Trump's daughter gave everyone a good look at it in her one-piece bathing suit -- and, trust us, you won't be disappointed when you catch a glimpse in our exclusive footage.

That's right ... TMZ obtained photos/videos of Ivanka and her children chilling on the sand and splashing around in the waters off Santa Teresa, Costa Rica.

An eyewitness tells us Ivanka's hubby, Jared Kushner, was there, too, but he's not seen in any of the snapshots or video clips shot Tuesday.

Back to Ivanka ... check her out with her family hanging out on the sand. At first, she's just standing there -- fully clothed -- observing people and looking out at the ocean.

Then Ivanka stands on a surfboard lying on the sand before stripping down to her one-piece and heading into the water with her board and her butt fully in the camera frame.

Once in the ocean, Ivanka shows off her surfing skills ... riding the waves on her board with ease at times. At other times, she falls into the water with an instructor pushing her into the waves. And, as an added bonus, Ivanka gives us a few more butt shots during her beach outing.