Jeff Bezos and Lauren Sanchez Pack on PDA at Foam Party on Megayacht

Jeff Bezos and Lauren Sanchez have changed the game when it comes to "foam fingers" ... 'cause the two stars played around at a foam party days before exchanging bling for their ring fingers!

The major couple was spotted on Jeff's megayacht -- the Koru -- off the coast of Europe Sunday ... partaking in a lavish foam party for Lauren's son Evan's 19th birthday.

JB and LS were covered in suds on the deck ... engaging in a little PDA a few days before their star-studded wedding.

Most of their bodies are covered in foam ... but, it seems Lauren's wearing just a tiny little bikini -- and Jeff's keeping up on his workouts, looking pretty darn muscular.

The whole group enjoyed a big dinner to celebrate Evan -- though we imagine the glasses were raised to the soon-to-be husband and wife duo once or twice.

If you don't know ... Bezos and Sanchez are getting married in Venice soon -- and sources with direct knowledge told us they're staying at the the Aman Venice, a hotel in the city. The hotel is fully booked up from Wednesday, June 25 to Sunday, June 29, and guests will be staying there.

There are conflicting reports regarding whether Bezos and Sanchez are getting married on the Koru or in a church ... so, we'll have to wait and see if it's a priest or a sea captain handling the ceremony.

Bezos and Sanchez got engaged in May 2023 ... and, we've put all their most important moments as a couple into a video timeline for you to peruse.