I know right! I would also think that a water balloon the size of ping pong ball isn’t going to pop, but will probably hurt like hell when you get smacked in the face with one.
There were a ton of rules when I was in scouts that were never followed. None of the scouts or parents even know the rules in most cases.
They work even better if they are frozen first and used in sling. The sling is optional of course:~)