March 22, 2023

Mary Sears: advancing ocean intelligence [Women’s History Month]

Posted by Laura Guertin

“The untold story of Mary Sears and her team of eccentric scientists who pioneered the oceanographic intelligence that revolutionized naval warfare in the Pacific during World War II and was instrumental in the United States’ victory over Japan.”  —  front book sleeve, Lethal Tides


If you are looking for a book to add to your spring/summer reading, I encourage you to pick up a copy of Catherine Musemeche’s Lethal Tides, Mary Sears and the Marine Scientists Who Helped Win World War II. This blog post is not formatted as a book review; instead, I’m hoping I can call attention to pieces of the narrative and link you to other resources that will interest you in learning more about the incredible accomplishments and leadership of Mary Sears.

The book does not only focus on the life of Sears! It includes the history of the Woods Hole Oceanographic Institution (WHOI), history of the Hydrographic Office, the background of WAVES, the importance of nautical charts to the war effort, and more. There is also an excellent discussion of the history of women not being allowed at sea – which included Mary Sears.



(*Sidebar – why does this tweet have to point out that her desk is “messy”? Would they have used that same wording about the desks of their other scientists? Just saying…)


For an overview, I highly recommend reading the Lethal Tides book review published in Oceanography, and Sears’ biography in this Smithsonian Magazine article Mary Sears’ Pioneering Ocean Research Saved Countless Lives in WWII. The book’s author Catherine Musemeche has given numerous interviews and appears on podcast recordings, from The Chris Voss Show Podcast to the American Shoreline Podcast Network and American Blue Economy Podcast (linked in tweet below).


“Sears was no longer at Woods Hole, where she had been sidelined by her male colleagues who sailed on Atlantis and collected her specimens while she stayed onshore. For the first time in her life, she was in charge.” – (Lethal Tides, p. 129)

There are several golden lines that I noted when I was reading the book – perhaps these highlights will pique your interest in diving into this excellent read, which again is broader than just the story of Mary Sears:

  • “Up until 1930, American oceanography was largely a self-funded science, led by wealthy male adventurers who could afford to underwrite the cost of worldwide expeditions.” (*until the founding of WHOI and Scripps) (p. 50)
  • “…how would the American military catch up with the oceanographic intelligence it needed when the seas had gone underexamined for decades?” (p. 94)
  • With regards to Dora Henry, the leading American expert on barnacles for over half a century, “There were two strikes against her… One, she was a woman, and two, she was a professor… She was thanked and informed that the navy wasn’t interested in her theory.” (p. 121)
  • “”The navy went to war without knowing enough about the oceans,” Sears later said.” (p. 146)
  • “Tarawa vividly and tragically demonstrated that minimum tide levels could not be taken for granted where coral atolls ringed the shore. Tides mattered, and on some days, tides were everything.” (p. 153)

There are entire passages and chapters I read with great interest, such as:

  • The beginning of Chapter 6 discusses the development of the bathythermograph (BT).
  • All of Chapter 12 is a fascinating exploration of the value of weather and tide data for the selection of the D-Day date.
  • Chapter 13 notes the importance of knowing and mapping the distribution of bottom sediments for predicting underwater sound conditions and planning landing operations, as well as the challenges with bioluminescence in a region.

There’s also a mention on page 59 in the book about Admiral George S. Bryan during his time as the officer-in-charge of the Hydrographic Office and publishing nautical charts. Admiral Bryan addressed the American Geophysical Union in 1942 about the burden his office now had responding to the ever-increasing demands of producing accurate nautical charts without the personnel and funding available to match the wartime demands. If there is an existing transcript to this talk, it would certainly be a fascinating read!

The nation was in a two-ocean war of global proportions, one being waged both above and deep below the surface of the sea, yet there was still much about the oceans that was unknown.” – (from Lethal Tides, p. 86, in a section discussing a Subcommittee on Oceanography meeting in 1943)

Her name carries forward

The life of Mary Sears has been celebrated in media outlets such as Harvard Magazine. When Mary Sears passed away in September 1997, her obituary was published in several locations, ranging from the Woods Hole Oceanographic Institution (WHOI) to The New York Times. Her name continues to be affiliated with prizes and awards in marine science, such as The Oceanography Society’s Mary Sears Medal and WHOI’s Mary Sears Women Pioneers in Oceanography Award. The U.S. Navy named an oceanographic survey ship in her honor, the USNS Mary Sears (T-AGS-65). We are so fortunate to have Catherine Musemeche celebrate the life and significant contributions by Mary Sears to our field – now, it is our turn to elevate these details in our classrooms, our textbooks, and elsewhere.

If you enjoyed reading Lethal Tides, you may want to check out other books that Catherine Musemeche recommends in this Wall Street Journal article, Five Best: Books on Unsung American Women of World War II.