Officials are preparing for oil from the Rena to arrive on Pukehina Beach in the Bay of Plenty.
Five metre swells are expected to buffet the Rena tomorrow and into the weekend, reports Newstalk ZB.
Salvors succeeded in their attempt to get onboard the ship's bow today and lash down containers in a bid to increase safety.
Up to 400 containers remain on the front part of the vessel.
High danger for divers
Jagged steel and crushing waves have made it too dangerous for divers to assess the wrecked ship Rena.
The stricken cargo vessel split in two in wild seas on Saturday night more than three months after running aground on the Astrolabe Reef near Tauranga.
The bow remains wedged firmly on the reef while the stern has mostly slipped beneath the waves, with only about a quarter above the waterline.
Maritime New Zealand salvage unit manager David Billington this morning said swells were continuing to prevent salvors from diving on the wreck to assess the damage of the break-up and partial sinking.
The current swell was about 2m, with a maximum wave height of 4m.
Mr Billington said the rough state of the swell was expected to peak tomorrow and subside over the weekend.
"The breaking up of the wreck has exposed a lot of jagged steel and the wave surges are causing containers and debris to shift around," he said.
"It is certainly not safe for divers to attempt to dive on the wreck in the current conditions."
Salvage company Svitzer yesterday dropped rigging technicians onto the front section of the wreck to secure containers on the bow.
Mr Billington said they would return today to ensure the containers remained as secure as possible.
Svitzer naval architects were developing plans for container removal from the front section, and assessing how best to access the bow.
The crane ship Smit Borneo was ready to return to the wreck when the weather conditions allowed.
Oil from the wreck was expected to reach Pukehina Beach tonight as clean-up operations continue.
A observation flight this morning showed an oil sheen stretching about 4km northeast of the Rena this morning.
National on-scene commander Alex van Wijngaarden said the heavy metallic sheen, between 10-60m wide, was part of a larger, lighter sheen stretching about 10km from the wreck.
The sheen was drifting down the eastern side of Motiti Island but did not appear to be reaching the shore.
Trajectory modelling predicted the oil was likely to reach Pukehina Beach and further east overnight.
"We have had unconfirmed reports of a small amount of oil stranding at Pukehina. We have sent a shoreline clean-up assessment team down to follow up on those reports and we have response teams ready to clean any oil they may find," Captain van Wijngaarden said.
About 60 oil spill responders in the field today, cleaning at Mt Maunganui and on Matakana Island.
"We also continue to get a significant amount of support from iwi volunteer groups, who are also doing a fantastic job."
Debris and container clean-up operations were continuing today, with Braemar Howells recovery teams working in several different areas both on water and on shore.
Mr Billington said considerable progress had been made at Waihi Beach with a significant amount of debris moved from the beach yesterday.
A total of 30 containers had been identified ashore in a number of locations.
More than 10 vessels would be recovering containers and debris today, including two specialised barges with excavator arms to tackle floating debris.
Braemar Howells aimed to begin removing 11 containers beached on Matakana Island today using both shoreline recovery, which involved moving containers by road, and on-water recover, which involved hauling some containers back into the sea to be lifted onto barges.
"Matakana Island is one of the areas that has borne the brunt of the debris washing ashore - there is a large scale operation there that will continue for some time," Mr Billington said.
Braemar Howells teams were also scouring beaches from Mt Maunganui to Papamoa, where small patches of debris had been located. Operations were also underway on Motiti Island and Waihi.
Wildlife teams were checking for affected wildlife between Mt Maunganui and Pukehina today.
Seven live and 31 dead oiled little blue penguins have been picked up this week, with the live penguins being stabilised at the Te Maunga oiled wildlife facility.
They will be transferred to Massey University's Palmerston North wildlife recovery centre for rehabilitation before they were released back to their habitats.
Boom maintenance teams would check up on oil-catching booms installed at Maketu, Little Waihi and Waitahanui yesterday.
Surf lifesavers had assessed all the beaches this morning, with swimmers encouraged to stay between the flags.
Two community meetings will be held today, at noon and 6pm, at the Tauranga Boys College auditorium on Cameron Rd.