The occupants managed to free themselves and alerted emergency services after discovering the family still clinging to trees.
Emergency services successfully rescued the family, who were rushed to the hospital.
Police found the young boy’s body inside the still-submerged car around 3.20 pm the following day.
Detectives from the NSW Police arrested the 38-year-old driver at Surry Hills police station in Sydney on Thursday.
The man now faces charges of manslaughter and dangerous and negligent driving occasioning death.
He is due to appear in court on 18 January.
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