NZ divers return from Tonga

Royal New Zealand Navy divers have left Tonga after finding and filming the wreck of the ferry Princess Ashika.

The navy divers were deployed after the Tongan ferry sank suddenly 86km northeast of the capital Nuku'alofa on August 5.

Defence personnel from New Zealand, Australia and Tonga located the site of the wreckage using a remote environmental monitoring unit.

Divers aboard HMNZS Manawanui were last weekend able to read the sunken vessel's name plate and positively identify the wreck using a remote operated vehicle.

Their commanding officer, Lieutenant Commander Andrew McMillan, said he was proud of their efforts and behaviour.

"The team have acted in a professional and compassionate manner, working under sombre and difficult circumstances."

The team and the ship was returning to New Zealand after completing their work to the maximum of their capabilities, he said.

After the ferry sunk 54 people were rescued. Two bodies were retrieved and the 73 remaining passengers are presumed to be drowned, trapped in the ferry, now sitting on the sea bed at a depth of 110m.

The cost of retrieving the vessel has been put at up to $25 million, more than double New Zealand's total annual aid to Tonga.

The Tongan government is expected to rule out salvaging the vessel.