In Crater Lake in Oregon there is a large stump of wood that has been floating in the lake for over 100 years. It has been bleached white by the elements and is large enough and bouyant enough to support a grown man.
Article on Wikipedia ETA :
A photo of a guy sitting on the "Old Man" can be found here And yes, yes, I spelled Oregon wrong. I live in Australia, can you blame me? I'm more familiar with oregano. :)