Salvors working on the Rena wreck today are securing the bow section in preparation for more bad weather.

Sea swells of 2-3m around the Astrolabe Reef, where the ship ran aground on October 5, are expected to increase to 4-5m on Friday with winds gusting up to 45 knots.

Rena's bow has little buoyancy and is expected to sink if it slips off the reef. Photo: Svitzer.

Maritime New Zealand salvage unit manager David Billington says salvors are doing everything they can to secure the foremost part of the vessel to the reef.

Salvors boarded the bow today and applied more lashings to containers that had come loose in previous bad weather.

'Salvors are being proactive in their approach – we were able to put more lashings on the containers and are doing the best we can.”

There is estimated to be between 360 and 400 containers still on the bow section.

MNZ salvage advisor Jon Walker says the bow is in an exposed position and has no buoyancy should it slip off the reef.

'We have to wait and see how the bow is affected by the weather,” says Jon.

'It will definitely deteriorate – it all depends on how the waves hit it.”

The 236m ship was torn in two pieces during a storm last weekend, sending more than 150 containers into the ocean.

On Tuesday, January 10, the ship's stern section began slipping down the reef and is now almost completely submerged.

Dive teams remain on standby waiting to assess the condition of the stern of the vessel, with sea conditions continuing to prevent operations.

MNZ national on scene commander Alex Van Wijngaarden says fresh oil is leaking from the wreck with a 600m long and 200m wide metallic sheen emanating from the reef.

'There is some new oil escaping from the wreck.”

Alex says another 10km long patch of oil is visible heading southeast of the wreck and a further patch of oil is located near Motiti Island.

'There is a different looking patch of oil south of Motiti Island.

'We think it may be a subservient algal bloom below the surface.”

MNZ trajectory modelling shows the oil is expected to hit beaches in Maketu and Pukehina eastwards overnight.

Thirty containers have washed ashore since the ship split in two and environmental clean-up specialist company Braemar Howells spokesperson Grant Dyson says contractors are making good progress at sea and on land to remove containers.

'We do not think there is much debris left at sea.

'What is there has been pinpointed and is well under control.”

On Wednesday evening the first three containers were lifted from the ocean using a crane and placed on the barge vessel, Sea Tow 60, and brought to shore for processing.

So far 11 containers have been removed from Waihi Beach and a further 11 containers remain on Matakana Island.

Grant says these will be removed by road or dragged back into the ocean and removed from the sea.

There have been a number of personal items from containers located on beaches and Grant says these are being put aside and will be returned to their owners as soon as they are processed.

MNZ acting manager of recreation and small craft Jim Lilley is asking boaties using Tauranga waters to be mindful of debris and containers.

'Any debris and containers are a hazard for the recreational fleet.”

Jim is urging any boaties to assess whether they really need to be out on the water, and if so, to travel at a safe speed and maintain a proper lookout for debris.