A West Australian coroner has reminded seafarers to let people know about their plans before they embark on a voyage after an experienced mariner died at sea in circumstances that remain a mystery.
Kevin Herbert Leban Miller was last seen leaving Kalbarri in his newly bought wooden vessel on February 12, 2009.
He intended to sail it about 200km to Shark Bay but has not been seen since.
An inquest last month heard Miller had equipped the former cray fishing boat, called the "Sea Hawk", with global positioning and emergency beacon devices, tools, a life raft and two dinghies.
"Something catastrophic happened, something happened quickly that didn't allow him access to those things," the WA Police missing persons unit's Detective Sergeant Stephen Perejmibida told the Coroner's Court.
Not having contact with his family was out of character, he didn't access his bank accounts and there was no evidence of criminality, the detective added.
Coroner Sarah Linton said in findings released on Thursday that based on all the evidence, she was satisfied beyond reasonable doubt Mr Miller died at sea.
She made an open finding as to the manner of his death, saying there was a possibility he had an unexpected health event and the boat sank afterwards.
"Given the various possibilities, I am unable to find that one is more probable than the others," Ms Linton said.
She said he did not follow the recommended practice of notifying the local volunteer search and rescue group, or a family member or friend, about his departure and predicted arrival in Shark Bay, so his absence was not reported to police for several days.
A massive search, at the time the largest in WA's maritime history, was eventually launched but the length of time that had elapsed reduced the likelihood that Mr Miller would be found alive, or at all.
"The death of Mr Miller is a reminder that even an experienced mariner can face insurmountable dangers when at sea," Ms Linton said.
"The circumstances of his death emphasise the need for those embarking on a sea voyage to let people know about their plans before they leave."