Ivanka Trump Gallivants Around Beach in Swimsuits with Model Karlie Kloss

Ivanka Trump's heating up the beach once again ... showing off her surf skills down in Costa Rica -- with supermodel Karlie Kloss by her side!

The First Daughter was spotted in the Central American country Thursday ... hitting the beach and hopping back on her trusty surfboard in the crystal clear ocean water.

Check out the pics ... Ivanka's showing off her bod in an orange two-piece -- soaked in the salty water but looking happy while walking along the beach later on.

In tow was her husband, Jared Kushner -- whose brother Joshua brought his wife, model Karlie Kloss.

It doesn't appear KK did any surfing like Ivanka ... instead hanging by the shore with her man -- wearing a black cover-up and a wide-brimmed straw hat.

No Secret Service in these pics, as far as we can tell ... though because Ivanka is the current president's daughter, she is entitled to a few agents.

As we told you ... Ivanka's been channeling her inner Kelly Slater this week -- making numerous trips to the water to shred the gnar.

While her skills certainly caught eyes ... so did her backside in a tight one-piece while she ripped through the waves.