Personally i would not call that a valid reason. There are plenty of unmanned bodies of water in the form of rivers, the sea, lakes etc. a child can even drown in a bathtub! Not filling a paddling pool in a park is a step too far in my eyes. Children young enough to be in danger should be with parents or guardians anyway. Older children should be able to get themselves out easily enough. I really do not want to bring this up, for fear of starting something i don't mean too, but the skate parks that have popped up all over the place ar FAR more dangerous than a pool of water. How there has not been a serious accident in these parks yet i'll never know. its all steel edges and slippery slopes, and none of the kids wear helmets! My point is, if thats fine to leave unmanned, why is a paddling pool such an issue?