Can anyone identify this SF book?

Awhile back I read a science-fiction book that took place 5000 years from now, in a world where industrial civilisation had run out of resources and collapsed, the seas had risen, and California was recolonised from Hawaii (which had returned to traditional ways).

The protagonists leaves his Havaiian-style village on the coastal isands of central California (the peaks of today’s coastal hills), and sails across the Inland Sea (which we recognise as the San Joaquin valley) on a quest. At several times he has a dream experience or vision of today’s world.

Anyone know what this book was? My google-fu seems to be lacking tonight.

Sounds like Spiritwalker but it’s the opposite of what you describe where a guy from our time is having visions of the Hawaiian guy’s life in the future. And it’s also not fiction, which may explain your lack of google-fu.

Actually, I think that is it. I knew there were visions of one time from the other, and I knew the book had a new-agey reputation about it. I had forgotten that anyone considered it to be non-fiction. So the author was recounting his own experiences of visons?

I enjoyed it and would like to read it again.

Thanks!