New Zealand navy divers in Tonga hope to return on Monday to the spot where the Princess Ashika sank and confirm that a wreck on the ocean floor is that of the ferry.
In all, 149 people are believed to have been aboard when the ferry sank 12 days ago. Just two bodies have been recovered, and 93 people are still missing.
New Zealand navy sonar equipment found what is thought to be the wreck last week in 110 metres of water.
The Manawanui arrived in Tonga on Saturday to act as a stable platform for a remote-operated vessel.
Lieutenant Commander Andrew McMillan says detailed sonar has been able to pick up debris like ropes in the area.