Hi fish head,
I suspect the individual you're betting with will want to see some science before he/she pays up. As such, you may wish to read the deliberations of the Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection (GESAMP) at
http://gesamp.imo.org/no62/conc.htm.
They conclude: "The greatest marine biodiversity occurs in the Indonesian archipelago and decreases radially from this area. The southern hemisphere has much higher biodiversity then the Northern hemisphere and Antarctica has higher biodiversity than the geologically younger Arctic."
Within this rather large Indo-Pacific region, a number of experts, including Raymond Anderson, an oceanography/chemistry professor at the University of British Columbia in Vancouver, believe the most biodiverse sector is around Papua New Guinea.
Palau is also in contention, and my acquaintance, Dr. Richard Pyle, Curator of Ichthyology at the Bishop Museum on Oahu, places the center closer to this island group.
In any event, the place is a very, very long way from the coast of California.
Best regards.
DocVikingo