Police say it may be some time before the wreckage of a plane that crashed into the sea off the Waikato coast is found because it is likely to have broken up and drifted in the current.
The bodies of the 2degrees chief executive Eric Hertz and his wife Kathy are believed to be inside the plane's fuselage, on the floor of the Tasman Sea in water about 60 metres deep off Kawhia, near Raglan.
Police say the twin-engined Beechcraft Baron probably broke up when it hit the water and debris on the surface could have drifted at least 15 kilometres.
The head of the operation, Sergeant Warren Shaw, says it is possible the wreck is at such a depth that it would be at the limit of the police's operating capacity.
He says they're relying heavily on the Navy and other experts for specialist equipment.
Mr Hertz, 58, and his wife, 64, were travelling from Ardmore near Auckland to Timaru in the South Island when they reported engine problems and disappeared off the radar about midday on Saturday.
The American couple had just gained New Zealand residency and were on their way to meet up with their adult daughter over Easter.
Police warned on Monday any recovery will be complex and could take some time. A 40-metre exclusion zone has been set up around the crash site.
Mr Shaw says while teams have found debris from the crash, they have not located the plane yet.
He says the Navy is helping with mapping the area where the wreckage might be and has provided equipment including unmanned submersibles.
Police and Navy divers would only enter the water when the search team has pinpointed the plane's location.
Staff will also be scouring the shoreline from a helicopter.
A Civil Aviation Authority spokesperson says if divers can't recover the wreckage that will make its inquiry much more difficult.
Mike Richards says insurers are likely to be involved soon and they will want to retrieve the wreckage.