How to control this guy at the pool while lifeguarding?

I'm a lifeguard at my neighborhood pool and there's this cute guy my age who'se there a lot and has recently found out that if he turns the hose on I get mad bc the pool water level is usually too high as is... so when it's my shift, he's like "ohhh I should turn on the pool hose" and he does, and like last time we were literally wrestling to try to turn the hose off and him try to keep me away from it and of course he won, since like 2 other littler boys were there and they were both on his side bc they like playing with the hose... and the hose is really obnoxious... so next time I'm lifeguarding and they turn on the hose, HOW can I get them to turn it off??????? I needa be more forceful but I don't know how.