Or could just say, if one of your kids is in the pool, regardless of other adults being in there/supervising their kids, you must sit pool side and supervise too.
This is what we do. I am thinking of altering it to the above being the rule for kids under 7 and over 7 (as long as they are competent swimmers) there must be one adult in the pool (or sitting on the edge watching) at all times but doesn't have to be the kids' own parents.
The problem with the 'hat' system is that other people simply aren't as tuned into kids that aren't their own. Also people with older kids just forget the level of supervision required by smaller kids. I have seen our friend let my toddler into the pool area and then go back to chatting while his competently swimming kids swam around him and he just forget about my toddler who was walking around the edge of the pool well out of the friends reach. So we also ask at the beginning of the day that no one let any children apart from their own through the pool gate. We also say upfront that if any kids under the age of 9 are in the pool an adult must be in the pool area. Some people are happy to let their 7-8 year olds in there alone and watch from outside the fence but I am not happy with that. We also talk to the kids first and make sure they know that when we say its time to come out they come, or there'll be no more swimming. This is so that you are not stuck negotiating to get kids out of the pool so you can go with one to the toilet for example....
This post has been edited by Kay1: 17/01/2013, 07:25 AM