Divers had also found a leak causing seawater to mix with lubricant oil within the ship, which salvors were also having to pump off, according to Maritime New Zealand.
As of 8am this morning, about 31 tonnes of oil had been transferred to the tanker Awanuia from the tank, which contains around 350 tonnes of fuel.
Underwater Association president Shane Wasik said the Rena would overshadow their conference this weekend, expected to draw about 1000 divers and underwater enthusiasts to the Bay of Plenty.
It was "spooky" the conference had been planned to coincide with the 130th anniversary of the sinking of the vessel Taupo - now a scenic dive site 12km north of Mt Maunganui - well before the Rena slammed into Astrolabe Reef on October 5.
"A lot of us have come to terms with it all. It's happened and we just have to move on. It's going to be years before the reef is anywhere back to normal, but the flip side is that divers really like shipwrecks," Mr Wasik said.
"If you got rid of the bad environmental effects of the oil, people would be excited about it. Looking into the future, that might be a drawcard for Tauranga and the marine industry."
He believed a wreck could create an artificial reef that could act as a new aggregator for fish life.
"Although it would take years to come right, it would be a bit of a boost in the end."
Mr Wasik plans to contact Costamare once salvors have pumped away the remaining 358 tonnes of oil on board and taken off the containers.
Maritime New Zealand's salvage unit manager, Jon Walker, said there were plans for the vessel, but the "real priority at the moment is the oil".
Salvors were having to purge air from the Rena's last full oil tank before pumping could begin.
Divers had also found a leak causing seawater to mix with lubricant oil within the ship, which salvors were also having to pump off.
Mr Walker said the stop-start nature of the pumping efforts had been "very, very frustrating" to salvors.
On the shore, a team of 320 people yesterday were involved in clean-up operations that have so far removed about 900 tonnes of oiled waste from Bay of Plenty beaches.
Mr Walker said that while sandy waste was being taken away for disposal at a facility in Hampton Downs, oil pumped from the Rena into two barges would probably be reused.
Meanwhile, the founder of a campaign on the website Change.org has called on politicians to hold Costamare entirely accountable for the disaster and make the company pay any extra funds needed for the clean-up.
"New Zealanders want to know if their politicians believe the amount legally required of Costamare is enough, or if they should contribute more to the estimated $100 million cost of the clean-up," Bay of Plenty-raised Rebeka Whale said.
The Government is considering prosecuting the company, which has apologised but refused to say if it will pay all costs. Talks between the two parties' lawyers continue.
The disaster has also driven a surge in people signing a Greenpeace petition calling for clean sources of energy. Yesterday, climate scientist Jim Salinger and actor Lucy Lawless joined the more than 100,000 signatories.
