Maritime New Zealand is unable to finalise its salvage plan for the Rena wreck until divers are able to assess the broken vessel's condition.

Divers are hoping to assess the now submerged stern section of the ship as soon as the sea conditions and wind drops around the Astrolabe Reef.

The stern section of Rena has fallen off the reef, while the bow remains in place. The bridge is almost totally submerged.

MNZ salvage unit manager David Billington says sea swells of 2-3 metres and 25 knot winds, along with sunken containers around the wreck, are making dive assessments impossible.

'It is still much too hazardous to dive the wreck – the ship is in a very exposed place and although it seems to be a flat and calm day at Mount Maunganui it is very different out at the reef.”

David says there is a lot of loose steel in the water and with wave surges pushing it in and out, the conditions are dangerous.

However, he says once the wind drops and the swell decreases, divers will undertake a survey of the wreck site.

'Divers are on standby and we have every intention of getting back out on the wreck site; the weather is meant to be settling within the next couple of days.”

This good weather follows an unsettled period, starting at the weekend with 7m swells that tore the ship in two before more swell on Tuesday saw its stern slip down the reef.

The bow of the ship remains in a similar position to when it ran aground on Astrolabe Reef on October 5, although David says it is in a badly damaged condition.

'The bow is badly damaged, but as far as we know it is not changed position.”

David says it is up to the salvage master to make the decision on whether or not it is safe to dive the wreck.

MNZ salvage advisor Jon Walker says there is no buoyancy in the back end of the vessel which is essentially underwater.

About 150 containers are estimated to have fallen from the ship since it broke apart in the storm at the weekend.

A further two containers fell from the ship on Tuesday and although the total number of containers in the water is not known, 49 have been identified and 30 have come ashore.

Braemar Howells operations manager Claudine Sharp says an extensive amount of debris was collected overnight, preventing further large amounts of debris coming ashore today.

'We are making steady progress at sea and on land. Today 12 vessels are working at sea, including two tugs loading timber and paper from the ocean onto the ST60.”

As of 3pm today, contractors had removed eight containers from beaches, with 30 estimated to have come ashore.

There are still 11 containers to be removed from Matakana Island.

Fresh oil is expected to begin washing ashore in areas southeast of Mount Maunganui from tomorrow onwards.

MNZ national on scene commander Alex van Wijngaarden says an aerial observation shows 12 patches of oil measuring 100m by 50m containing traces of heavy black oil.

He says it appears to be dispersing and based on the current trajectory will reach areas southeast of Mount Maunganui including Maketu.

Alex does say it is important people remember this is a much smaller amount of oil than what was previously released and will not result blackened beaches.

Booms are being placed at Little Waihi and Maketu in preparation for fresh oil.

Alex says there are currently no reports of fresh oil on Motiti Island, or around Mount Maunganui and no further oil is seen to have leaked from the wreck.

The beach clean up volunteer programme has been reactivated with about 100 volunteers working on Waihi Beach today.