Replying to Life guard pranks

so the people i work with smeared hot pepper all over my whistle (yes it was as sexy as it sounds) and even got the head lifeguard to tell me that i dont use it enough, just to get me to use it in front of them.  This in response to me filling a bunch of reserved signs that get used everyday for swim lessons with water so they'd be a pain the ass to move.

so now its pretty much open war at my work and im trying to think of good ways to exact my revenge..

so far i've got ideas like filling their sunblock with vinegar/prawns/smelly shit, enlisting their swim lessons people to mess with them and the other standard prank stuff like sneak in their car and put baby powder in their a/c.

so help me out NS, i need some good stuff to get back at these fools