Summer/Beach

Soon-to-be divorcée Katharine McPhee did a little advertising on the beach in Cabo this weekend ... showing off her tan-lined body less than two weeks after pulling the plug on her marriage.

As TMZ first reported, McPhee said in her divorce docs she and hubby Nicholas Cokas were separated for seven months before she was spotted locking lips with "Smash" director Michael Morris.

Nicole Scherzinger did her best Jessica Alba impression over the holiday weekend, showing off her incredible bikini body aboard a yacht in St. Barths.

At 35 years old, the former Pussycat Doll still has several lives left in her.

Justin Bieber luxuriated on a yacht in Monaco Saturday.

Bieber looked more ripped than ever as he took a break from the Monaco Grand Prix, kicking back and drinking a brewski.

As we reported ... sources very close to the singer tell us he's off Sizzurp ... in no small part because it screws up his workout routine. One source very close to Biebs says in the past 3 weeks he's been like a different person.

Cutting out Sizzurp ... it does a body good.

Whether it's a modest little dinghy or an insane yacht -- these celebrities taking to Instagram and are bragging about shoving off and soaking in the sun is style... Check out which stars strapped on their sea legs and hit the open waters in style!

Ahoy!