This is hardly the first -- or second, or third, or infinitieth -- time we've seen Kylie Jenner in a bikini. But this is the first time we've seen Kylie rock her own bikini line.

The 18-year-old fashion designer showed off more than a little cleavage wearing a strappy yellow and black bathing suit with "KENDALL + KYLIE" emblazoned all over it. "Shooting Kendall&Kylie swim for TopShop. Coming soooon," Kylie captioned the photo.

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Kylie also shared behind-the-scenes footage from the shoot, including a clip of her showing off her best poses while listening to "Hold Up" from Beyonce's new album, Lemonade.

"Bikini sneak peeks on my snapchat," Kylie wrote. So, to her Snapchat we went!

...and what we found were some very revealing -- and potentially NSFW? -- Snaps.

Body-ody-ody.

Kendall Jenner also cameoed, wearing a slightly more demure white two-piece.

Kylie recently made brother Rob Kardashian "so happy" when she made peace with his fiancée, Blac Chyna. Get the scoop on the new -- and VERY surprising -- "best friends" in the video below.