MacBook Pro 13" Waterproof locking case?

I'm about to go to college and I'm looking for a laptop case that will provide superior protection for my 13" MacBook Pro. I want something that will lock with a combination lock (definitely not keys, I lose keys), is waterproof and is portable as I will be on a college campus. I'm willing to spend a decent amount of money but I just can't find anything that really fits my specifications. I've searched dozens of websites but cannot find anything that would really work.