"Gloomy day of paddling with mah girl Spencer Johnson," she tweeted of her pal.
Though the weather may have been "gloomy," Jenner appeared to be having fun. In the shot, the 17-year-old Keeping Up With the Kardashians star gave the camera a big smile while posing on her paddleboard. Jenner proudly showed off her slim beach bod in a pink bikini top and black wetsuit pants.
In May, the reality star appeared in her first swimsuit campaign for Agua Bendita. But Jenner has her sights set on being a Victoria's Secret model someday.
"It's always been kind of a dream of mine," she told E! News in April. "It's a very great thing to do, and it's something I'd love to do."