Lower Hutt police said they received a call at 1.00pm after a passerby spotted a car with a man sitting on its roof in the harbour just north of Eastbourne.
A white Nissan Cefiro stationwagon had fallen more than two metres on to rocks near Days Bay Eastbourne.
The crash was caused by driver inattention and speed was not a factor.
The driver, in his 40s, was heading north along Marine Drive when he was distracted and his car left the road at a point before Days Bay. The driver got out of the upturned car himself with only a small cut or bruise on his face, and it is likely he will face charges.