Emily Ratajkowski was on vacation somewhere beautiful, and you can bet she packed a few swimsuits for the trip. While visiting a hot spring, the star slipped into a black one-piece with a plunging neckline, which she wore with layered necklaces. Though the front of her Peixoto swimsuit was revealing, the back was even sexier. It featured a scooped back and a cheeky thong fit that showed off Emily's assets. Her friend even playfully left a muddy handprint on Emily's buttocks. Scroll on for a closer look at the star's sultry one-piece.