Among all the voyeuristic joys available in locker rooms, jock ass is in the top two. If you count each cheek as a number, then ass is number two and three. So what else is on the list?
Number one is dick. Or technically number one is the phone number of the guy with the dick you want, but that requires conversation, not pure voyeurism. Then we have ass and ass. Followed by chest, feet, foreskin, jockstraps, pissing, sucking, ejaculation and now I've lost track because the locker room has devolved into a fucking orgy. Or at least the hope of that is what goes through my mind whenever I'm in a locker room.
Ass watching is pretty perfect though because by definition the guy totally can't see you looking because to this point in evolution, nobody can actually see through their pink eye. Yes, it's known as a brown eye, but I think it should be called a pink eye now, otherwise poor pink eye is stuck just meaning conjunctivitis.
Just remember if you ever get totally caught staring at ass (like if you forget some of those tricky mirror angles, or someone whips around really fast and you don't turn away because why would you stop looking at fine ass anyhow!?) then here's the plan: beg to hook up with the guy.
Remember begging can be classy and confident. Just keep the drooling to a minimum. Because drooling is totally cute as a metaphor for sexual hunger, but in practice it's also one of the reasons why wearing flip flops in a locker room is a good idea.