Kiwi Timothy Mitchell crushed to death in US storm

A loose boat slammed into the harbour, killing Timothy Mitchell. Photo / Supplied

A New Zealand man has been crushed to death in a fierce storm off California.

US media reported that Timothy Mitchell, 39, a harbour patrol officer died while trying to save a dive boat from sinking.

A statement from the Los Angeles County Sheriff's Department said Mr Mitchell jumped from the boat to get to safety as it came "perilously close" to striking rocks in the harbour

Two deputies attempted to rescue him from the water but were unsuccessful. "He became lodged between the vessel and the rocks under the turbulent waves and could not be reached," the sheriff's department said.

Friends and family of Mr Mitchell posted tributes to him on Facebook, praising his courage.

His brother, Matthew, wrote: "For anyone out there who knew my awesome brother Tim and don't yet know the news, Tim died yesterday in a storm on Catalina island while on duty with the harbour patrol."

The Catalina Scuba Luv group, where Mr Mitchell was an instructor, wrote: "Scuba Luv is suffering the loss of longtime instructor-son, Tim Mitchell to a furious Nor'easter storm.

"Tim courageously attempted to save the King Neptune as she parted four mooring lines and was swept to Step Beach. The resultant crash took Tim's life. We are sending our condolences to his family, en route from England and New Zealand."

A photo of Mr Mitchell on his brother's Facebook account

Mr Mitchell moved to the US in 2000 to pursue a career in diving, the California Diver magazine reported. He was also a reserve firefighter for the City of Avalon.

John Etheridge, who owned property on the island, witnessed the incident and told ABC7 Mr Mitchell was trying to save the King Neptune vessel when he was swept overboard.

"It was the most horrible thing I've ever seen." Mr Etheridge said. "When (the boat) hit the beach, it hit with a great deal of force and hit a couple of times and he was just thrown overboard," said Etheridge.

Etheridge told ABC7 a crowd of up to 40 people saw the incident from shore and frantically tried to save Mitchell, but were unable to.

Mitchell's former mother-in-law, Jennifer Morris, told ABC7 she was devastated. "I couldn't believe it at first. Being here now is making it harder. It's all become a reality," Ms Morris said.

ABC7 said a houseboat owner, identified later by coroner's officials as 53-year-old Bruce Ryder, also died as a result of the storm.

Another man found floating in the harbour, Bruce Ryder, 53, later died at hospital.