The Doublooner — Weyman Jones

A former combat pilot is trying to find a meaningful life after a failed marriage and forced retirement from the Navy. He becomes part of a high-tech search for lost Spanish treasure off Key West, Florida. A murder at a lavish party involves him with a boat gypsy who seems to have information about a treasure site, along with an exotic seductress who has a deadly agenda. He is attracted to a local divorcee, whom he inadvertently puts at risk before the action reaches its climax in a standoff at sea with hand weapons.