lets say you jailbreak an ipod and you need to take it to apple. and it wont sync so theres no way to get installer off. can you drop it in water and they'll never know? and you get a new one?
If it won't sync, use a dif PC, USB port, or put your iPod in DFU mode and restore *don't ask me how,search*
But yeah they will know. There is a little piece of paper that turns purple or some color when exposed to water*located in head phone jack* so don't do it.
Don't get the dock connecter part wet either. It corrodes and turns a green color. That's another way they know it got wet and it'll void the warranty.