Thanks for the comments guys. Old champagne bottle makes a lot of sense! The bottle isn't mine (it's my sisters) and I think the coral will stay on it alright.
Hi Folks, This one was brought up by a diver somewhere around Key West. It was covered in coral and you can see residual bits of it still stuck to the glass. I'm guessing it's from a wreck given the sheer number of them in the vicinity of that area. No distinguishing marks to speak off, green...