The New Zealand Police dive squad is currently attempting to locate the missing bodies of 2degrees CEO Eric Hertz and his wife Kathy, following their plane crash off Kawhia Harbour on Friday.

Traveling in their twin-engine Beechcraft Baron, the pair have yet to be found off the coast, with the depth of the wreckage, 60 metres below water, making the recovery process longer than hoped.

Waikato Police have "extensively" searched the harbour area so far, but despite their best efforts no bodies have yet to be found.

"We've got sonar equipment which can identify where the plane is and with the plane at 60m under water it is very complex (as) we need to determine what the structural integrity of the plane is in order for us to see if we can get the bodies back as safely as possible," Marcus Lynam, Waikato Police inspector told the press.

"With the plane 60m down its very difficult to get any divers down at that level.

"It's a very complex operation.

"We believe NZ Navy have dived to a depth that deep, however it's very difficult to get down."

But as police remained determined to locate the missing bodies, the Hertz family braced themselves for the harsh reality.

"It doesn't seem to be, based on all the conversations we've had with the people in charge of what has happened, the Civil Aviation (Authority) and police, it doesn't look good, we should say," Johanna Hertz, Hertz's sister, told Radio New Zealand over the weekend.