The stern section of the Rena appears to have stabilised for the moment after it started sinking this morning.
About 75 percent of the stern - the larger of the ship's two sections, split apart in bad weather- is now completely underwater.
Svitzer Salvage spokesman Matthew Watson said the stern was perched on the edge of the Astrolabe Reef at a 45-deg angle.
It appeared to have stabilised in that position and it was not clear whether it would move further.
There was a lot of debris in the water, mostly timber from the ship's cracked hull, and a "mild'' amount of oil was visible, Mr Watson said.
Salvors managed to land a helicopter on the front section of the boat, which was relatively stable in its position on the reef.
It took about 45 minutes for the stern to sink to its current position after it started tipping at about 9am.
"Essentially she has listed right over to the starboard side and the rear section has pulled back, so she's sunk backwards.
"At the moment about 75 per cent of the rear section is under water - the accommodation quarters are completely submerged other than the mast and a small section of the section of the bridge. The front section of the stern - where it had split - is pointing upwards towards the sky.''
It was not clear how many containers went down with the stern as an unknown number had washed overboard in the last couple of days.
Salvors were holding a meeting to decide what to do next.
"There was a sense of inevitability that this would happen, it's not a surprise. Now the assessment process continues and very shortly the salvors will know what their next moves will be.''
Papamoa Surf Life Saving Club head lifeguard Shaun Smith, who has been looking at the Rena everyday since it ran aground, was concerned that with the wind blowing directly onto the beach today, further containers and debris could come ashore.
Tauranga Mayor Stuart Crosby said he had been warned there was a "strong possibility'' the stern would sink, so the news had not come as a shock.
"There is a small concern about whether it will settle on the sea bed and if this will create extra debris or if this will aid in the possible recovery of the Rena.''
Mr Crosby said his personal view was that the sinking of the stern was positive as it was off the reef.
"If it's in reasonably deep water it could become a diving attraction. This is just another step in the Rena saga that would eventually happen. Maybe out of sight out of mind but this could be a positive thing for us.''
Ngati Ranginui chairman Hui Kakahu Kaue told the Bay of Plenty Times yesterday there were spiritual, cultural, physical and emotional implications for iwi should part of the Rena sink.
"Physically, in terms of food we suffer, especially those in Motiti [Island]. There will be a long-term disadvantage and effect on them.''
Steve Penn, of the Waikato and Bay of Plenty Marine Recreational Fishers Association, said most fishers had accepted it was likely that the ship would sink.
He said he not believe the sunken hull would have a negative effect on the environment.
He did not think it would be much different to incidents in which battleships were deliberately sunk for fishing and diving purposes.
"Probably a lot of fishermen will say `great, a little bit more hapuka'. It could be a good thing,'' Mr Penn said.
Green Party oceans spokesman Gareth Hughes said people would have the opportunity to dive to the wreck if it was left where it was.
In its current position, the stern would sink to a depth of about 90m, meaning divers would be able to reach it. Most divers can go to only half that depth.
"Although it would have been ideal if the stern could have been towed in and cleaned first, the salvors said it wasn't safe to bring it in. Safety has to be paramount and we have to defer to the experts,'' he said.
Transport Minister Gerry Brownlee is heading to Tauranga and will hold a press conference at 3pm. Environment minister Nick Smith is also on his way.
The Bay of Plenty Regional Council's harbourmaster has directed that all vessels to stay at least 200m clear of all containers from the Rena, as well as any salvage vessels working on the response.
Boaties were urged not to go onto the water unless it is necessary.
"If the trip is unavoidable, vessels must proceed at slow speed, keep a good lookout and travel through the area in daylight only.
"The debris field is extensive, its movement is unpredictable and could extend further.''
- Matthew Theunissen of APNZ and Bay of Plenty Times staff