The 36-year-old reality star donned a teal one piece swimsuit in the image, pairing the low cut beachwear with a pair of denim mini shorts.
The mom of three appears to be inside the front of a boat with friends. Other sailboats are visible in the background of clear, blue seas. She captioned the picture, simply, "boating."
In another snap, posted earlier on Saturday, the Keeping Up with the Kardashians star posed with her younger half sister Kendall Jenner while on the balcony of a beach house.
"Off duty supermodels. Oh wait, not plural," Kardashian wrote, referencing the 19-year-old's career.
The girls were similarly dressed in jeans and button down shirts, both also donning black belts and sunglasses.
How Scott Disick May Have Blown a Second Chance with Kourtney Kardashian
Kardashian recently split from longtime boyfriend and father of her children Scott Disick in June.
Disick's continued his string of strange behavior since the breakup on Saturday, sharing a photo that seemingly alluded to the relationship's end.
In the image, Disick holds a place card that reads "Scott Disick Guest."
"When you realize the grass isn't always greener," he wrote.