Jeff Bezos and GF Lauren Sanchez Yacht Vacation in St. Barth's

Jeff Bezos is living the good life -- and it's showing -- down in the Caribbean with his GF, Lauren Sanchez.

Almost a year after going public ... Jeff and Lauren are spending the holiday down in St. Barth's, aboard David Geffen's massive 450-foot superyacht, the Rising Sun. They're definitely looking ... comfortable during what seems to be a dual celebration.

Besides Christmas, it was Lauren's birthday last week. So, twice as many reasons to go anchors aweigh on Geffen's pride and joy ... which they REALLY enjoy, apparently. They also toured the South of France on it back when Jeff went 2 buttons for the win.

Looks like Bezos might squeeze in some work on this trip, too -- comes with being the richest man in the world, we guess.

The couple has a whole group with them, including Russian-American businesswoman Dasha Zhukova and some of her young, attractive friends.

Hey, if ya gotta talk shop ... might as well do it aboard a $600 million dinghy.

Since coming out back in January, both Jeff and Lauren have finalized divorces from their respective exes.