I think I've noticed that when the kids start playing in the water, the wasps leave for awhile. It gets hard to count them with all the choppy water. Do a few cannonballs and see how many are left
My daughter was stung in a pool when she was three. She didn't know what the wasp was and picked it up on her wrist. Knowing her she was trying to pet it or something, she neglected to tell me the specific details in the midst of the aftermath and all the crying. Since then; however, I have managed to teach her that wasps are not to be feared. She has taken that lesson to heart and now lets them alone even when one gets in the house.