Kylie Jenner posted this Instagram photo of herself and big sister Kendall goofing off at the pool on Tuesday, and after spending several hours the previous day shooting a new Pac Sun ad, the girls seemed to be having a blast relaxing.

We already knew Kendall was Teen Vogue's September cover model, but the 18-year-old starlet officially made her U.S. Vogue debut with a full-page photo shot by Patrick Demarchelier. Kendall wears Alexander Wang in the fashion spread, and thankfully, there's no mention of her role on Keeping Up With The Kardashians.

Kendall recently landed a Givenchy campaign, and she's also featured in the new issue of Du Jour magazine. She's everywhere! The racy pic, snapped by Bruce Webber, shows Kendall on her back with a super hot male model on top of her. Kylie and several others are taking pictures of the couple, and Kendall remarks that this isn't so different from her day-to-day life.

"Its hard to imagine a day when the cameras wont be there, because its all we know," she tells the mag. "Even before the show, when we were babies - four or five years old - wed be walking red carpets with our dad. I dont think we really remember a time before the cameras," Kylie added.

What's next? Kendall jetted off to Chicago on Wednesday morning ... check out photos of her at the airport in the gallery below!