B.B.
IF you are certain that they are not residents of the complex where they are swimming then you can call the police b/c they are trespassing. I know that sounds harsh but it just might do the trick. You could even give them a warning that you are going to call the police. This might stop the behavior all together. I know it is frustrating and as a mom you worry about their safety. And I would not be above talking with their parents about their behavior. If you have asked them to stop doing things that are dangerous and they continue then their parents need to be informed. Also I would want to know if my kids were being a pain in the neck and if they were some where that I was not aware of. I bet even money that if they are swimming in their clothes and not swim suits then their parents do not know where they are. Do not be afraid of making the kids mad, you are protecting them by letting some one know of the dangerous behavior. I hope tis helps.