so, it appears the road is his, but was used "since 1918" with permission of previous owners for access, and is the only safe access for that area. In California, the property lines end at high-water's edge. I guess that's the same for people who live on lake lots maybe? According to the SF article, the next step is eminent domain vs Mexican Land Grant.
http://www.sfgate.com/bayarea/article/Vinod-Khosla-wants-30-million-for-Martins-Beach-6847689.php
Actually the statute from the 70s clarifies the public beach goes up to the vegetation line. The state constitution required the legislature interpret article x as liberally as possible to ensure access was preserved.