Boxer shorts and a Tee shirt. My Tee has "Do it in a van" written on the front and a picture of the van I presume you are supposed to do it in...
I don't actually like the top much, but it was just handy when I got in so on it went.
Mind you the more I think about it, the more appealing the thought of buying that van sounds... let's go to the beach and do it!!