While working for the Navy, Craven helped pioneer the use of Bayesian search techniques to locate objects lost at sea (Bayesian search theory). Craven's work was instrumental in the Navy's search for the missing hydrogen bomb that had been lost in the Mediterranean Sea, off the coast of Spain in 1966. Craven's next large accomplishment was in the search for and locating of the submarine , which had disappeared in deep water in the Atlantic Ocean west of Portugal and Spain.