Rihanna Strung Out & Board in Hawaii

1/20/2012 5:15 AM PST BY TMZ STAFF
Rihanna in a black thong bikiniRihanna was hanging by a few small threads in Hawaii yesterday -- testing the structural integrity of a tiny black thong bikini, while sunning her 23-year-old buns in the ocean ... on a paddleboard.

Whatever floats her butt.