Case of the Ostentatious Otters

When a dead SCUBA diver is discovered during their road trip vacation to Monterey, CA, Zack, Jillian and the two corgis, Sherlock and Watson, become embroiled in a race to discover what the diver had been doing when he died. Compounding their investigation is the presence of a group of playful otters, who just so happen to be using what appears to be gold coins as tools to open shellfish. Are the two events related? Could the deceased diver have located a sunken treasure ship off the coast of Monterey?