Slawson said four lifeguards were on the pool deck and four camp counselors in the pool, which has seven lanes and depths of three to five feet.
"He was somewhere in the middle, maybe a little closer to the deeper end of the water," Slawson said. "From what I understand, he did not know how to swim."
She said the camp group, which she did not identify, had a permit to use the pool.
Police Lt. John Walker said the director of the camp program was walking into the pool area when she saw the child under the water.
"At that point, she yells to the counselor, and the counselor dives right under the water and lifts the kid up and puts the kid on the deck," Walker said.
Slawson said that a lifeguard administered CPR and that the boy was taken to Children's Hospital of Philadelphia, where he was listed in critical condition.
"We're not sure if he had a medical incident, got kicked in the head, took some water on and went under," Walker said. "There are a whole lot of scenarios that could have gone on here."
Slawson said the pool was in compliance with city rules that require one lifeguard for every 30 swimmers.
Walker said the incident was under investigation, adding: "We're fortunate that people acted very quickly."
Contact Vernon Clark at 215-854-5717 or firstname.lastname@example.org.