He's posed as a model for Calvin Klein underwear. And pop star Justin Bieber skipped swim trunks in favor of a just pair of white CK briefs as he showed off his impressive wakeboarding skills and toned physique while out on the water in Miami yesterday.

The 22-year-old was enjoying some down time with friends, including actress Ashley Benson, on a yacht over the Fourth of July weekend while in-between stops for his Purpose World Tour. See more photos below...