I wear a size 9 shoe as well, though my feet are on the narrow side. I wear an 8-9 (M) in the Beach variety. (There's also a Men's size listed, I think it's 6-7.) There is plenty of side to side wiggle room, though, so that size might work for you, too. I tried the next up size on, and it was ridiculously huge on me. Good luck!
jenny