Plane crash: Boaties told to stay back

Sonar images have mapped where the twin engine Beechcraft Baron was lying near Gannet Island. Image / Supplied

Boaties have been asked to stay 500m from the site where the plane belonging to 2degrees chief executive Eric Hertz and his wife Kathy crashed off the Waikato coast while divers search for the bodies.

The couple's bodies are believed to be trapped in the wreckage of the upside-down plane, 56m below the surface.

The navy's dive support vessel, HMNZS Manawanui, which was due to arrive at the site this morning, would be the focal point for the recovery operation.

Incident controller, Sergeant Warren Shaw, of the Waikato Police search and rescue squad, said one of the challenges faced by the team was determining whether Mr and Mrs Hertz remained on the plane.

"To be able to do this successfully we need to be able to conduct our operation unhindered so we're asking boaties and masters of vessels to ensure they respect the 500m radius exclusion zone around the crash site off Gannet Island."

Mr Shaw said while the recovery was going on, local iwi had placed a rahui on the area.

"This is a mark of respect for those in the water and requires people to refrain from carrying out any action in that water and is in synergy with the objectives of our operation.

"Because the plane is upside down we haven't been able to confirm the location of the bodies. To that end police need to have a range of contingencies in place so in the worst case scenario, if they aren't, we can locate them."

The team's priority was recover Mr and Mrs Hertz "in an as dignified manner as possible", Mr Shaw said.

"People can best show their respect and support for the bereaved family by observing the Rahui and the 500m exclusion zone."

The Manawanui's commanding officer Lieutenant Commander Kerry Driver said once they were at the site, police and the dive team would make an assessment on whether to try to retrieve the bodies or the wreckage.

That call would be made by police, Lt Cmdr Driver said.

The vessel had a recompression chamber, which would be needed because of the depth the divers would go to. Commander Driver described the depth as being on the limit of the drivers' capabilities.

There was also a crane on board which could lift the aircraft from the seabed.

The couple had been on their way to visit their daughter in Dunedin when their plane ditched at high speed on Saturday.