Sacramento County Sheriff's Sgt. Shaun Hampton said the man's 10-year-old daughter called 911 on Friday and said her father had jumped in the San Joaquin River in Isleton without a life vest to rescue her brother.
Hampton said a U.S. Coast Guard crew located the boat and the boy floating in the frigid, murky water. He initially didn't have a pulse and was taken to the hospital where Hampton said his conditions improved as of Saturday.
Two other children who were on the boat were reunited with family.
Hampton said the water has been moving fast due to heavy rainfall and runoff.