There are times and places for people to be nude - one of those is not at a family barbecue! I hope you took her aside and politely told her that her actions were not appropriate with family present. It would have been vastly different if that was your family's pool, and she was alone by herself - and at least one parent was there AND AWARE of what she was doing. However, since it's already done, talk to the adult members of the family who actually owns the pool and tell them that, unless they have some "hard and fast" rules about swimming "in the buff" in place next time while there are other children present, you'll have to think twice about attending another BBQ party at their house.
Are you kidding me, there have been studies showing that children exposed to family nudism at a younger age are more pron to be family oriented when they grow up, are less likely to develop sexual problems as young adults, and have a better self-image. If you don't believe me google it, but I can tell you from experience that nudism has changed my life for the better.
P.S. Most of those kids there haven't even hit puberty and are not sexually attracted, so that makes the chances of babies go all the way down to zero!!!
I wouldn't let my Kids (if I had any) go swimming in the nude in front of others (Kids and Adults). If they want to do that I'd make them wait until they were 21 and older and let them go nude with other adults. I feel that Kids should not be exposed to that sort of behavior.
I agree with sleepless-in-illonois ,inapropiate behavior ,asking for problems ...
NONE of those children should be swimming nude!!!!!!!!!!!! NONE!!!!!!!! Where there no adults present??? Letting male and female children swim together nude is just telling them that it is ok. Do you want your daughter swimming nude with other men. This kind of behavior just tells the child their private parts really dont have to be private and everyone is welcome to see. Are you anxious to become a grandfather?? You may become one before you or your daughter is ready. It sounds as if your whole family needs a wake up call. I really dont know any parent who lets their child (regardless of age) swim nude at all let alone with others people around. I am an RN and where I am from if someone came to my place of employment and told any of us nurses or any of the doctors that story, we would call the authorites and report child abuse. You and all the other adults that where present and let this take place should be ashamed.