JEFF BEZOS & LAUREN SANCHEZ Sun's Out, $500 Mil Superyachts Out ... Let's Work On Our Tans!!!

Jeff Bezos and Lauren Sanchez are wasting no time enjoying his new $500 million superyacht ... slipping into some swimwear to tan on the deck of the huge ship.

The billionaire and his boo are on the massive vessel for the first time, tooling around Mallorca, Spain, and basking in the rays on the boat's sprawling deck.

Jeff stripped down to some blue trunks, and Lauren busted out a pink bikini for their maiden voyage Tuesday aboard the Amazon founder's new 417-ft long, three-mast vessel dubbed the Koru ... a Maori word for new beginnings.

Hard to say what's bigger, the boat or their smiles.

Of course, Jeff should be in a good mood aboard his newest toy ... the yacht was finally delivered this week after some lengthy delays, including that little controversy in the Netherlands.

Jeff and Lauren had the ship's captain sail around the island, stopping in a small bay.

They didn't step foot off the floating village, but when ya drop half a billion on a boat ... that's to be expected.

The 2 happiest days in a man's life are when he buys his yacht and when he sells his yacht ... and Jeff looks happy here, though he might prove to be the exception to this rule.

Click here for info about our online advertising practices.