Justin Bieber wears nothing but wet Calvins after jumping into a glacial lake in Iceland

The 21-year-old singer is really taking his role as the face - and body - of Calvin Klein to a new extreme wearing nothing but his tight whitey's to plunge into icy water in Iceland on Tuesday.

While the act of jumping into a lake formed by a melted glacier is fearless enough, the 21-year-old was even more fearless when he had completed his freezing swim - emerging in the wet and clinging underwear.

Waking across stone riverbank to give a much more covered up pal a high five, the smiling star showed off his slim but toned tattooed physique.