The War Beneath the Waves: Mary Sears and the Navy’s Oceanographic Unit

On Display 3/4/2025 – 4/9/2025

After World War II, Mary Sears was promoted to lieutenant commander and served as officer in charge of the Navy’s new Division of Oceanography. She retired as a commander in the Navy Reserve in 1963. 

Mary Sears posing behind stacks of work, January 1, 1960. Photo courtesy of Woods Hole Oceanographic Institution Archives

During World War II, navigating the Pacific Ocean’s perilous tides and currents posed a constant challenge to the U.S. Navy. To update their maps and intelligence, the Navy established an Oceanographic Unit in 1943. The team of scientists was led by Mary Sears, a marine biologist commissioned as a lieutenant junior grade in the women’s division of the Naval Reserve, the WAVES. The unit’s intelligence reports successfully predicted tide times, analyzed undersea conditions for submarines, and identified landing beaches. Sears and her team saved countless American lives and helped change the course of the war in the Pacific.

Between 1943 and 1945, Sears and her team delivered 20 intelligence publications to the Joint Chiefs of Staff, who used the research to make strategic decisions about the war. This Joint Army-Navy Intelligence Study (JANIS) chapter that Sears prepared contains detailed oceanographic studies and charts that advise on the region.

Joint Army-Navy Intelligence Study of Southwest Japan, JANIS 84, Chapter 3 (Mary Sears), August 1944. Records of the Naval Intelligence Command

View in the National Archives Catalog
Admiral Nimitz praised Sears for her leadership and contributions to the Armed Forces in this commendation letter. He acknowledged the urgent requests she received from the Joint Chiefs of Staff, for which she would sometimes calculate through the night.

Commendation letter issued to Mary Sears by Admiral Chester W. Nimitz, May 20, 1946. Records of the Bureau of Naval Personnel

View in the National Archives Catalog

More online resources:

Military Records Research: Research by Branch

Pieces of History: WAVES: It’s a Woman’s War Too!

The Text Message: Mainbocher: Designer of the “Best Dressed women in the World”

The Unwritten Record: Spotlight on Veterans: Navy Women in Parachute Rigger Training

History Hub: Army and Air Force Records

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