Police say the search for a boatie missing north of Auckland is likely to stretch throughout the weekend.
Extensive searches have so far failed to find Donald Ravenscroft, 73, who was last heard from on Sunday while on his yacht in Mahurangi Harbour near Warkworth.
Police say Mr Ravenscroft may have swum after his dinghy when it drifted away from his launch.
The dinghy was later found tied to a tree across the harbour.
A police spokesperson, Sergeant Bede Haughey, says the disappearance is not considered suspicious and the search is operating as a recovery mission.
He says a group of volunteers, made up of family and friends, will search alongside police and Navy dive squads throughout the weekend.