This thread offers some great advice. I copied some of it below. I guess I was naive, but before I read this thread, I thought drowning at summer camp almost never happens.
http://www.dcurbanmom.com/jforum/posts/list/46916.page
There were two very distinct types of camps. I would characterize them as lax and excellent, to be honest. The lax ones let the lifeguards watch, and spent their time chatting or yelling at the kids. The exellent ones all had the same T-shirt on, identifying them as past of the camp. They stationed themselves around the pool. They had a system to separate the non-swimmers from the big part of the pool (with the deep end) and one staff member was in the water herself, making sure young kids didn't get into the big section. They seemed competent and on the ball, and I would not have had a problem letting a 6 year old go swimming with them.
The "lax" ones, I would have had a problem with. I will say that I think te snager is greatest for the younger kids -- the 3 and 4 year olds -- with this group.
Before letting my children go swimming in a public pool with a camp, I would ask to see a copy of heir supervision policy for non-swimmers, and check out the pool to see what kind of trouble a non-swimmer could get into. For instance, if the entire pool is only 4 feet, a non-swimmer who is comfortable going under water isn't going to get into a lot of trouble, especially if the lifeguards and camp staff are provideing decent supervision as to no rough horseplay, no diving, etc.
Let the camp staff know you trust them but you want to know that they have good safety procedures in place, and find some likeminded parents who might have similar standards, take turns visiting the first few days they go to the pool if you can to verify that the procedures are being followed.