What would you do?

What is it that even a perfectly well-mannered, mild-tempered kid goes absolutely crazy and all rules, self restraint, and manners go OUT the window when you put kids in or near water? Last Friday our friends came to visit from Tampa. I was trying to think of something we could do in the evening before dinner so I thought we could go swimming for a little while. Honestly, I also didn't feel like giving Rya a bath and just wanted to white trash bathe her for the evening...nothing like killing two birds with one stone, right? Anyway, we get there and it's a ZOO. A madhouse! Kids everywhere. We watched them for a little while and they were having SO much fun, but I started getting panicky. I'm not a big fan of kids and more were showing up by the minute. I figured I needed to get Rya in, rinse her off, TRY to play for a few minutes and get out before all the elementary aged kids in BWB showed up. So off we went. I'm holding Rya on my left side and walking down the stairs when BAM! something hard and fast hit me on the forehead (inches from the baby)! I mean I knew I was walking into a danger zone, but for Pete's sake. I look down and see this dive stick torpedo thing at the bottom of the pool next to my foot. I got NAILED in the face with a dive stick torpedo thing! Here's what it looked like, except it had some sort of cartoon character face on the top:

Problem: I didn't see which out-of-their-mind kid threw it. So, I bent down, picked it up and laid it outside of the pool. I watched closely to see who came to pick it up and spotted an overweight 5/6 year old boy grab it and take off. No apologies, no excuse me, no ceasing of the "game". It took me a little while longer to figure out who owned him and when I finally figured it out I was VERY discouraged. Three ladies had met up at the pool to let their kids play to allow them so social time. They were relaxing, talking, having a couple of beers...unfortunately, they weren't very attentive to their hellions. My heart sunk b/c I didn't want to approach them (yes, I'm a chicken), but by this time, my forehead was swollen and throbbing. I practiced what I would say a few times and realized that I was too angry to say anything, so I didn't. We just left. Of course, the next morning I woke up with A LOT of nicer ways to address the situation, but the moment had passed. So my question to you is this: What would you have done?