The weather, which has been the single largest obstacle to clearing the Rena wreck off Astrolabe Reef, has been enlisted as a demolition aid.

Salvors are making cuts in the remaining steel in the bow section and leaving the weather induced wave action to knock it into the water, says Maritime NZ spokesman Reece Golding.

The remains of the bow section of Rena taken on April 2, 2013.

The remaining wreckage stuck on the reef has been whittled down to a small section that now breaks the surface at the reef about 25km off the coast of Mount Maunganui.

Reece says helicopters have been unable to land for some time and have instead been putting down a skid to allow salvors to transfer onto the remainder of the wreck.

'They would put a skid down to allow people onto the forward section,” says Reece.

'It is pretty precarious.”

The 236metre ship grounded on Astrolabe Reef on October 5, 2011. It split in two in January 2012 with the aft section later sinking down the reef.

The Resolve Salvage and Fire is contracted to reduce the remaining wreckage to one metre below the lowest low tide. Reece says there is about 300 tonnes to go.

From the debris field the salvors have recovered about 624.6 tonnes of steel, from an estimated 1000 tonnes that can be recovered.

The debris is being located by divers using GPS to map the locality, and removed by crane and barge.

Divers have in recent weeks shifted their focus from clearing the reef to removing the last problem containers from the sunken aft section of the ship, which is lying further down the reef.

The concerns are three containers of ferrosilicon, two containers of plastic beads and one of copper. The beads are in containers in No.4 hold at a depth of 19 metres.

It's labour intensive work, and divers have been removing bags of beads by hand when they can, says Reece.

A floating boom on the surface prevents loose beads from escaping and they are being scooped up using whitebait nets.

There were 1368 containers on board Rena when she struck Astrolabe Reef at 17 knots.

Since then 1031 have been recovered. Most of the 337 containers outstanding are thought to be in the aft section of the ship which is lying in deeper water at a dive depth that requires recompression chambers, and lengthy decompression stops.

Many of the remaining containers are part of the mixture of steel wreckage that comprises the debris field on the reef.

Getting to the beads is difficult says Reece as salvors have had to cut through sections of the ship and get past furniture, 'hundreds” of trampolines, and tyres.

In the last week, Wednesday, Thursday, Friday and Sunday were dive days when 135 intact bags were recovered by hand from the relocated container.

Once the first bead container has been emptied and as weather permits, Resolve will continue removing debris from the hold, and try and locate and assess the state of the second container of beads.

Removing debris from the hold is described as like trying to do surgery at around 20 metres underwater with a 280 tonne crane.

The final stages to reduce the bow will remain on hold as the work on hold four continues.

A sonar image of the aft section sunken on Astrolabe Reef.