Ivanka Trump's surfing enough this week to consider going pro ... 'cause she was back out in the ocean off the coast of Costa Rica, sporting another bikini.
The First Daughter hit the beach with a few pals ... walking into the crisp ocean blue with her board under her arm -- ready to carve up a few waves.
IT's wearing a small black two-piece bikini this time around ... a lot like the orange number she wore earlier in the week during her beach afternoon with her model sister-in-law, Karlie Kloss.