If a container ship grounded off Tauranga sinks, it will be the largest wrecked in New Zealand waters to date.
Cracks are appearing in the 236-metre-long Rena which grounded on the Astrolabe Reef off the Bay of Plenty coast on 5 October spilling hundreds of tonnes of heavy oil.
A historian at the Ministry of Heritage and Culture says the Rena weighs 37,000 tonnes gross - far more than the next largest wreck, the 22,000-tonne Mikhail Lermontov which sank in 1986.
Gavin McLean says with modern navigational tools shipwrecks are less common, but more serious because of their size.
Dr McLean says the Rena will be the worst maritime environmental disaster because the fuel leaking is thick bunker oil instead of the coal and diesel used in the past.
