It is what we call around here a "Camel"
Built by the
Navy in WW2, they were used as fenders between big ships when rafted, and also for floats along the top of an anti-submarine net stretched across Narragansett Bay.
Ours (and that one looks like it's the same), are made of creosote-impregnated yellow pine timbers, strapped with
steel bars and rods that go all the way through. We still have a few floating around and
washing up on beaches around here--scary to think about bumping one in the night.
The nonprofit I
work for has removed a few. The link I copied goes to a blog post I wrote about the
removal of one on our company site. Enjoy!
PS, if the link doesn't
work, you may have to copy and paste, or perhaps a mod will fix it: I'm terrible bad at nerd stuff.
http://www.cleanbays.org/portfolio/camel-removal/