Dream Walker by Larry Prosor

Fired from his job at an Indian casino and armed with a dolphin amulet gifted to him by his Noqoto Indian grandfather, student archaeologist Peter Martinez is on a mission to save Rocky Point, California from an oil giants development plans. But when his exploration of the sacred coastal land leads him to an ancient burial cave in the side of a cliff, a wave knocks him into the water and he wakes up on the beach—more than 300 years in the past.