Canoeing with my 5d

I plan on renting a canoe this weekend for a canoeing adventure and would love to bring my 5d for some photography. I've canoed before and the water I'll be in will be relatively calm but I'm concerned about that one expensive slip that puts me and my stuff in the water. Does anyone have a nice, cheap homemade solution that will protect my camera when I'm not using it? I know I could throw it in a bunch of trash bags but without some floatation I think it would sink like a stone.