Salvors are braced for the worst-case scenario of Rena breaking-up and spilling more oil with gale-force winds and swells of up to 5m forecast to hammer the Bay today.
They have stopped pumping oil and sealed the Rena as severe weather is expected to peak tonight with 45-knot winds - also raising the risk of more containers falling overboard.
At 7.15 this morning, there were 3m swells around Rena but no reported change to the ship or the containers on board overnight last night.
Salvage efforts on board the stricken ship were suspended yesterday as the threat of heavy sea conditions made it unsafe to continue working.
Svitzer salvage master Drew Shannon said that salvage crews had been removed from the listing vessel as a safety precaution.
He said the risk of endangering personnel or jeopardising the environment through pumping activities had forced their hand in terms of quitting the ship.
"We decided, based on weather forecasts ... that we will suspend our operations. We will ride out the weather.
"The safety of life is paramount," he said.
The suspension of salvage operations meant there was no further progress made in sealing the coffer dam to give access to the final starboard number five tank. No oil has yet been pumped from the tank, which contains 358 tonnes of heavy fuel oil and is submerged below the waterline.
Maritime New Zealand salvage unit head Kenny Crawford said achievements had been made during the recent period of fine weather. Four of the five main heavy fuel oil tanks have been emptied and more than 1000 tonnes of heavy fuel oil had now been recovered from the Rena.
Mr Crawford said the bad weather would bring with it swells capable of further damaging the already crippled vessel and therefore the tanks and air vents aboard the Rena were being sealed in case it split.
"This should help limit further release of oil in the worst-case scenario of the ship breaking up," he said.
Captain Shannon said there was no way to know if this storm could be the one to finally snap the ship.
"We are always prone to mother nature. We can't rule out what damage [the weather] could do to the ship.
"We will risk assess this on an hourly basis. We have to standby and wait on this weather," he said.
There is a further risk that more containers could be lost overboard as the swells pick up offshore and Captain Shannon said the salvors were yesterday trying to fit tracking transponders to the accessible dangerous goods containers and other containers in case they fall from the ship.
Metservice weather ambassador Bob McDavitt has placed a severe weather watch in place for the Bay of Plenty, with gales and large swells expected to peak tonight.
National on-scene commander Mick Courtnell said there was a chance more oil could leak from the stranded ship in the rough conditions.
"Exactly where [the oil comes ashore] will depend on wind and tide conditions. We are remaining vigilant and will be ready to respond if and when this happens," he said.
Mr Courtnell said that, to date, volunteers have given just over 11,000 hours of their time to help.
Volunteer co-ordinator Pim de Monchy said volunteer numbers were up slightly over the weekend with 200 on Saturday and 160 on Sunday. So far there have been 3732 participants.
He said volunteers were still needed, although the cleaning ranks had once again been bolstered by army personnel in Maketu and Matakana and now also by community probation workers at a special site in Te Tumu.
Mr de Monchy stressed that, except for main beach from Mauao to Tay St, the beaches remained closed.
He'd had reports of people swimming at closed beaches where the oil concentration was still strong, and even people digging for shellfish in Papamoa.
"We've seen a few people swimming around the Papamoa Surf Club, as well as digging for tuatua. [They were] popping them open, wiping the brown sludge off the tuatua and eating them. That's just ridiculous behaviour."