Lauren Sanchez rang in 2025 the only way she knows how -- living large! She and fiancé Jeff Bezos cruised into the New Year aboard his $500 million superyacht 'Koru,' making waves during their luxurious St. Barts escape.

The former entertainment reporter was living her best yacht life, basking in the sunshine with Bezos and their glamorous friends ... flaunting her curves in a skintight white cover-up that showcased her jaw-dropping cleavage.

Lauren was all about good vibes, sipping on a drink and basking in the tropical glow -- even catching up with her ex, NFL Hall-of-Famer Tony Gonzalez, who was also onboard.

Making it a true family affair, Lauren’s eldest son, Nikko Gonzalez, who she shares with Tony, was also chilling on the vessel.

It's been all systems go for Lauren and Jeff recently -- their holiday whirlwind took them from the Aspen snow to the Caribbean sun ... and if their New Year’s festivities are any hint, their wedding’s gonna be the event of the century.