UPDATED 4.28PM: Communities in California and New Zealand are in mourning after an expat Kiwi died during a storm on Catalina Island.

39-year-old diver Tim Mitchell was trying to save a boat which had become detached from its moorings during the storm when he became stuck between the vessel and rocks.

Chris Constantine, publisher of California Diver Magazine, says Mr Mitchell was a well-liked person.

"His loss has touched so many lives, here in the dive community and in the local community of Avalon and Catalina Island," he says.

"It's a really a sad thing to have happened to us."

"Tim is the kind of guy that would go out of his way to help people and that's been proven both with his professional history, all the way through to the heart of who he is."

"He just wanted to help people."

Tim Mitchell moved to California from New Zealand in 2000.