The girl and her family, from Bridgeport, were swimming in the northern part of Lake Mohegan in Fairfield.
The girl and three other children started having trouble staying above water, and relatives went in to save them. But the girl, who has not been identified, slipped from her mother's grasp and went under.
"We were quick on scene," Fairfield Police Chief Gary MacNamara said. "We had fire personnel, police personnel, ambulance personnel. They all went in the water right away, with no real equipment, trying to feel and drag their legs and see if they could make contact with the girl. It's hard, because it's very murky, lot of debris in the water, very difficult."
A police diver found the girl, but she had been submerged for at least 45 minutes.
Swimming is only allowed in the southern stretch of the lake, not in the area where the girl drowned.
"Our hearts are with the family," MacNamara said. "It's a sad day."
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