A trust that was trying to preserve an historic Auckland ferry that sank last week has asked police to investigate film footage that may show what caused the mystery sinking.

The Kestrel, which plied between Auckland and Devonport from 1905 to 2002, sank at its mooring at Wynyard Wharf overnight on Monday last week.

Kestrel Preservation Society chairman Mike Alston said the vessel had a float-switch alarm that should have sent texts to two people as soon as any water got in.

"The strange thing from our point of view is that the alarm never sounded," Mr Alston said.


"There were organisations, including commercial organisations, that wanted us moved because it [the boat] was just in their way.

"The council wanted us to move it. We wouldn't, because if we moved it to a backwater they might have said out of sight out of mind, it can just rot there. So we told them it was only insured while it was tied up to the wharf and if we move it, it's your responsibility."

Asked whether he suspected that someone might have deliberately interfered with the vessel, he said: "I don't think anyone I've been talking to would be so stupid or so evil to do that, but it's strange, and it's worth investigating."

"On the balance of probability, it's probably just natural causes," he said.

"The alarm worked reasonably well when we didn't need it, then when we did need it, it didn't work. I don't have a conspiracy theory."

Society treasurer Hugh Gladwell said he had asked police to look at footage from "a number of webcams" in the area.

A spokesman for Panuku Development Auckland (formerly Waterfront Auckland) said Panuku had asked Ports of Auckland Ltd to supply any film footage it had of Wynyard Wharf.

Mr Alston said the vessel's insurers were also trying to find out what caused the sinking because they faced "a six-figure job" to remove the wreckage.