The couple got engaged in January. Since then, Timberlake has been busy filming 'Runner, Runner' opposite Ben Affleck in Puerto Rico.
But his fiancee joined him in the tropical location, and the couple were able to enjoy some fun in the sun, reported Us magazine.
"We're both adventure junkies. She probably is even more than I am," said Timberlake.
The 31-year-old actor-singer is, however, afraid of sharks. "I had never gone scuba diving before I met Jessica and she actually talked me into it. And I said, 'I got one rule, if we are on that boat and I see a shark I'm not going in the water, it's not happening.'
"Ironically, we're sitting on the boat... The first thing I see is a shark! And I just had this moment where I looked at her and was like, 'Ahh, whatever,' and we went in. It was actually really unbelievable."