The nine-year-old was pulled from the river at Dearne Valley Park, Hoyle Mill.
It is thought the boy had been playing with friends at the park but it is unclear how he ended up face down under the water.
Police officers confirmed he was still in a life-threatening condition at Leeds General Hospital.
He was rescued by passing horse rider Louise Bennett, 40, of Tredis Close, Monk Bretton, as others stood and watched.
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