Five days of searching by surface and shoreline crews and police divers have failed to turn up anything.
Mr Hawke (70), an experienced sailor, fell overboard while sailing on Roys Bay on Thursday evening. He was unable to re-board the boat and disappeared underwater.
Yesterday's police dive squad search was stood down about 2.30pm after an area covering 350m by 450m near Eely Point - identified as a probable location for Mr Hawke's body - was completely covered.
Coastguard Wanaka Lakes president and marine adviser Jim Talboys said some parts of the search area had been covered twice "to be absolutely sure", but searchers found no sign of Mr Hawke.
"We believe that we actually have a person to recover and we believe we know the area he's in, so we now need to bring some more equipment in to find him," Mr Talboys said.
The search operation was now completely in the hands of the police, as from a coastguard perspective, "there's nothing more we can do".
The specialist underwater sonar equipment police plan to bring in is the same as the sonar used to locate helicopter pilot Morgan Saxton's body when he crashed into Lake Wanaka in 2008.
