Paulina Gretzky flew all the way to St. Barts to celebrate her birthday ... but don't fret -- Wayne's smokin' hot daughter packed the tiny bikini!!!
Dustin Johnson's baby mama just touched down in the Caribbean with the superstar golfer and some friends ... and it didn't take long for her to bring the birthday cakes to the ocean.
Paulina rocked an itty-bitty swimsuit and took an amazing photo ... and even Johnson himself had to gawk at the view, saying, "So beautiful!"
It's bday No.