"It's a tragedy," Recreation Commissioner Susan Slawson said. "Right now he is critical. We're praying for the family, we're hoping for the best."
Slawson said the camp, which has a permit to use the pool, had about 24 children in the water along with four counselors when the incident happened. In addition, she said, four lifeguards were on duty.
She said the boy, who is unable to swim, was near the middle of the pool, which ranges from 3 to 5 feet deep. He was not wearing a life vest.
It was unclear if he had a medical condition.
"We had the necessary procedures in place," Slawson said. "We're going to do everything we can to figure out what happened and how we can prevent this in the future."
Police interviewed children, camp counselors and lifeguards as part of their investigation.
"We're not sure if the kid had a medical incident, got kicked in the head, took some water on and went under," said Lt. John Walker, head of Southwest Detectives. "There could be a whole lot of scenarios."
Slawson said it was the first serious incident reported at city pools this year.