'He lights up the room wherever he goes' ... Jennifer Kwong and Adam Griffiths.

In shock ... Jennifer Kwong with Adam Griffiths. Photo: Facebook

An Australian tourist has drowned off Hawaii's Kauai island while trying to rescue his best mate who was knocked into the ocean by a large wave.

Adam Griffiths, who moved from Australia to the US and lived in San Francisco where he was the manager of a mobile app company, was holidaying on Kauai with his fiancee, Jennifer Kwong, and their friend, Brian Baker.

They were exploring the island's rocky coast on Friday when Baker, a 47-year-old triathlete, was hit by a large wave and dragged out to sea.

Griffiths, 46, jumped in to save his friend, but drowned.

Griffiths' body was recovered on Saturday, but Baker, from Vallejo, California, is yet to be found and rescue services suspended the search on Tuesday.

Kwong, who planned to wed Griffiths in September after six years together, watched the tragedy unfold.

Griffiths and Baker were described as kindred spirits and it did not surprise Kwong and their friends Griffiths died trying to save his mate.

"He lights up the room wherever he goes," Kwong told the San Francisco Chronicle.

"He's a very lovable man. I'm in grief.

"I'm in shock. I lost my fiancee and a really good friend."

AAP