Emergency services were called to Boulevarde, Woy Woy around 11am on Sunday after a vehicle left a quay and entered a channel.

NSW Police said the vehicle was believed to be a small green SUV.

Officers from Brisbane Water Police District have established a crime scene and are coordinating the search for the vehicle alongside Marine Area Command, NSW Maritime and NSW Ambulance.

Authorities said the driver is believed to be the sole occupant of the vehicle, according to information provided to police.

NSW Police have issued an urgent appeal for information.

As investigations continue, anyone with information about this incident is asked to contact Crime Stoppers on 1800 333 000.