KEY POINTS:
The boat in which two children drowned when it suddenly sank near Waiheke Island was missing one of its bungs, police confirmed last night.
Detective Senior Sergeant Simon Scott confirmed that a bung was missing from the wreckage but he said it was not known whether it was missing at the time of the accident.
"It's very simple to see that one of the bungs was missing at the time of the inspection," he said.
"If that was missing at the time [of the accident], we don't know.
"We haven't drawn any conclusions as to whether that was the cause of the accident. We're going to wait until the end of the inspection, which is going to take some time."
Bungs are drainage plugs which screw into the bottom of the boat. They are usually removed when the boat is taken out of the water to allow excess water to drain out from the bilges. If one was missing it would not necessarily be noticeable while the boat was moving, but once stationary, the boat would start to take on water.
Erina Rowles, 8, and her brother Travis, 5, died when the 7.3m aluminium launch sank in the early hours of Anzac Day.
Lindsay Rowles this week told the Herald how his wife Tania tried to save their children as the boat sank stern first after taking on water near Tarahiki [Shag] Island, off Waiheke.
Two family friends on the trip also survived and Mr Rowles said they clambered on to rocks after trying to dive down to the wreckage, 6m below the surface.
He said it was possible an old anchor rope wrapped around the propeller as he tried to motor towards land, dragging the boat under the water stern first. Mr Scott said that theory was being considered.
"That's been suggested and we'll look into that. There's a number of other things we want to look at as well and we'll take it all into account."
Erina and Travis were trapped in the boat cabin as it went down.
Mr Rowles said his wife woke them when the boat started taking on water and fitted their lifejackets as he tried to move closer to the island.
The boat tipped and the four adults were thrown into the water.
Mrs Rowles suffered head injuries as she tried to get into the cabin as the launch sank.
Mr Scott said an autopsy confirmed the children had drowned. He said the police investigation would look at all factors, including the time of night, alcohol and use of lifejackets.
A funeral for Erina and Travis will be held today.
Police say they have given the family time to grieve before continuing to speak to them next week.
Maritime New Zealand is also investigating the accident.
The boat was blessed yesterday, as police worked to establish how the tragedy unfolded.
