It is understood the man's son raised the alarm about 5pm after his father failed to return from a fishing trip.
"We have also had several people contact us reporting sightings of Mr Kang over the weekend, and based on this evidence, the indications are that he has gone into the water," McNeill said.
The land search for Kang has now been scaled back, but aerial searches over the coastal area with the Police helicopter will continue over the next few days.
"We want to thank everyone who has come forward with information and sightings of Mr Kang," McNeill said.
"As the public can appreciate, this is a very hard time for his family and we are doing all we can to help them and find him."
Police earlier said that Kang's car - a 2011 white Toyota Prius - was found at the Bethells Beach car park.
Police also appealed to members of the public who were at the beach over the weekend for any sightings of Kang.
Anyone with information is asked to contact Waitemata Police on 09 839 0697.