Hm, I run a local pool this summer (I blame pregnncy insanity for the decision to take THAT on...), and I'd want moms to let one of the employees know so they could address it with the child, and their parent as necessary. I know that in our facility a simple, 'I'm sorry, but you aren't welcome here if you can't follow the rules,' works pretty well. If it doesn't, we have a really big tall scary looking Sheriff a phone call away.

We have 'no splashing' rules, and enforce them within reason. If there are just a couple kids, and it's a simple little spatter here and there, I really don't care, but with a bunch of kids, or even one who isn't big enough or happy with the minimal splashing, it's over. The splashing makes it hard to see everyone in the water, as well as being overwhelming and scary to some really young swimmers. it also tends to tick off parents...
On a 'mom' note, I took my ds to the pool this afternoon (yeah, a day off and I spend free time where I work?) He's 11 months old and really comfortable in the water, but I was pretty open about protecting him from some kids splashing and playing with the waterballs nearby. When one didn't want to listen, the lifeguard on duty pulled him out of the pool for a few minutes. Earlier in the day, they'd kicked out two slightly older boys for tormenting people with the pool noodles. I'd address the concerns (even after the fact) with the people who manage the park so they know to monitor more closely.