The body is not believed to have been in the water for more than a few hours.
Given the tide was on its way out at the time, it is unlikely he floated from the inner harbor area to where he was found, police said.
No one fitting the man's description has been reported missing to police so anyone who thinks they might know this man is urged to call police on 0274 367 561 or email jessica.phuang@police.govt.nz