Remarkably clear photos of a ship wreck that contains up to 73 bodies have been released by the Royal New Zealand Navy.
The Tongan ferry Princess Ashika sank earlier this month.
It rests in 110 metres of water, northeast of the Tongan capital Nuku'alofa.
It was formally identified yesterday by a remote operated mini-submarine (ROV) by a team on HMNZS Manawanui.
The ROV spotted human remains but pictures of that were not released.
The navy say that while surface conditions were not favourable, they managed to launch the submarine.
The water clarity was very good and this allowed the team to be able to conduct a good, thorough search of the sunken vessel.
One side of the Princess Ashika is obstructed and the ROV was unable to see into the passenger compartment.
The vessel is sitting flat on the seabed and appears to be intact.
One of the images captured shows an upside down ambulance that had been donated by an American Methodist Church charity for use in a government hospital in Vavau. Much of the cargo, spilt out is wood intended for the same hospital.
The ROV entered the cargo hold to provide evidence for a royal commission of inquiry.
Earlier Tonga Police Commander Christopher Kelley said human remains had been seen on the wreck.
"The ROV operation did identify evidence of human remains around the site but the Navy staff operating the underwater camera took a respectful and non-intrusive approach to maintaining the dignity of the wreck site and those remains," he said.
"No identifications were possible and those images will not be released."
Manawanui and the dive team will now return to New Zealand.
Tongan police say they can now "confidently say" that there were 129 people on Princess Ashika when it sailed.
They confirm 54 survivors, two bodies and 73 people unaccounted for.
Of the 73 they say that 67 are confirmed as having been on board.
Salvage expert Keith Gordon says New Zealand has the technology to recover corpses from Princess Ashika but the question was who footed the bill.
"If it was rich Americans, they (relatives) would go out and finance it," he said.
Mr Gordon – who has his own remote operated vehicles – is best known for his book Deep Water Gold on the salvage of a wartime wreck, the RMS Niagara, off the Hen and Chicken Islands.
New Zealand and Australian salvage workers used makeshift equipment to recover 555 gold bars from a strong room deep in the hull of the ocean liner in 1941 – at a depth of 121 metres.
They used a human observer in a diving chamber, watching through glass portholes to direct the use of claw grabs by an operator on the surface, but Mr Gordon said that kind of real-time observation could now be done with ROVs.
One possibility would be for the passenger lounge to be torn open so that the bodies could float to the surface.
"If they are in the upper structure, that could be relatively easy to open up," Mr Gordon said. "You could just tear the top part open. . . the bodies would just float up".
"No doubt, a ROV could even recover a number of bodies or assist to do that," he said. "You have an articulator arm on the front – we've used them for that type of thing before, to bring a body up".
Some overseas police forces, such as in Scotland, actually had an ROV specifically for recovering bodies.
"For smaller ROVs these days, that depth is no big deal".
The larger of two ROVs used by his company, SeaRov Technologies, can operate to 330m depth. Mr Gordon said that it was possible that the Tongan Government might reduce costs by simply declaring the wreck as a sea grave, and block efforts by families to cut loose their dead relations.
He thought it unlikely anyone would pay to salvage the ship, even though that might give definitive evidence of its seaworthiness before the sinking.
New Zealand Diving and Salvage managing director Dougal Fergus has said that for human divers to work deeper than 50m would require use of an oxygen, helium and hydrogen mix and compression and decompression chambers.
Divers must spend at least two weeks in the chambers before the dive and the operation could take at least a month.
Adding the cost of a ship and crew would mean a bill of between $750,000 and $850,000 a day, putting the total bill up toward $25 million.