The driver of the vehicle was found close to the scene of the incident on the Portaferry Road in the early hours of Saturday.
Police said the driver sustained “minor injuries” and was taken to hospital.
The PSNI shared an image of the vehicle on social media on Saturday.
“Top marks to the passing motorist who spotted this vehicle on the Portaferry Road earlier,” the post said.
“Yes easy to see now, but at 2:30am when dark, with driving rain and higher tide not so obvious.
“Police were first to arrive with officers entering the water to check for casualties, and were swiftly joined by specialist teams to widen the search.
“Thankfully the driver was located nearby, and was treated for minor injuries prior to being conveyed to hospital.
“Fantastic teamwork all round, and great appreciation to our blue light friends in the NIFRS (Northern Ireland Fire and Rescue Service), NIAS (Northern Ireland Ambulance Service) and HM Coastguard.
“None of this possible of course without the speedy actions of you the community.”