The towed camera sled, which was fabricated by J. L. "Jac" Hamm of Naval Research Laboratory's Engineering Services Division, is housed in the National Museum of the United States Navy. Buchanan had located the wrecked hull of "Thresher" in 1964 using this technique. The classical book on this subject "The Theory of Optimal Search" (Operations Research Society of America, 1975) by Lawrence D. Stone won the 1975 Lanchester Prize by the American Operations Research Society. Assume that a stationary object is hidden in one of n boxes. For each box formula_3 there are three known parameters: the cost of a single search at location formula_3, formula_5; the probability of finding the object by a single search at location formula_3 if it is at this location, formula_7; and the probability that the object is at location formula_3, formula_9. A searcher looks for the object. They know the a priori probabilities at the beginning and update them by Bayes’ law after each (unsuccessful) attempt. The problem of finding the object in minimal expected cost is a classical problem solved by David Blackwell. Surprisingly, the optimal policy is easy to describe: at each stage look into the location which maximizes formula_10. This is actually a special case of Gittins index.