Halloween Help Needed

I'm having trouble coming up with a Halloween costume that I can wear for work tomorrow. As a lifeguard, I'm quite restricted in what's practical and acceptable for the lifeguard stand. I was thinking a hat with a shark's fin, but of course I don't have one of those. I thought maybe a luau type costume because I could just wear a hawaiian shirt open over my guard suit and a flower in my hair. However, the only hawaiian shirt I own is a) three sizes too big (*she happily reports*) and b) still packed in a box somewhere. I suppose if I get very industrious I could stop in at Wal-Mart, but I'm not thinking I'll find one there. Then again, if I do, it'll probably be on the summer clearance rack. Woohoo... bargains!

Any suggestions??