Deep Six is an adventure novel by Clive Cussler published in the United States by Simon & Schuster in 1984. This is the 7th book featuring the author’s primary protagonist, Dirk Pitt. Deep Six opens in 1966 aboard the refitted liberty ship San Marino on its way from San Francisco to Auckland, New Zealand. The ship is carrying more than eight million dollars worth of titanium ingots as well as a mysterious passenger who goes by the name of Estelle Wallace. Wallace is actually Arta Casilighio, a former bank teller at the Beverly-Wilshire bank who embezzled more than $120,000 and is making her getaway. Unfortunately, for her and the rest of the crew, a group of Korean seamen who came aboard as last-minute crew replacements have hijacked the ship and its cargo, and conveniently dispose of Wallace and the crew by paralyzing them with poison in their food and dropping them over the side into the depths of the ocean.