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Nina Agdal

The 21-year-old swimsuit stunner had a ball as she frolicked in th waves during a photo shoot on the beach for OP.

Celebs Rock Monokinis

Yahoo Celebrity

It's not a two-piece, it's not a one-piece, it's a ... monokini! Stars from Mariah Carey to Rihanna to Kendra Wilkinson have been donning the trendy swimsuit lately on both beaches and the small screen. Check out the sexy summer style and decide for yourself: Hot or not?