Maritime Archaeologist, Wisconsin Historical Society
UW Majors: Agronomy, Horticulture, Plant Breeding & Plant Genetics
For more than three decades of underwater exploration, her work has taken her from Caribbean cave systems to the wreck of the USS Monitor off the coast of Cape Hatteras to the Titanic for National Geographic’s 100th-anniversary coverage. In 1994, she founded Diversions Scuba, Wisconsin’s first technical dive shop, which she still owns, and she was inducted into the Women Divers Hall of Fame in 2014. Most recently, she’s made headlines for locating and conducting an ongoing study of more than a dozen ancient Indigenous dugout canoes in Lake Mendota.
Thomsen chose to attend UW–Madison in part to spend more time with family — including her grandfather, Art Thomsen ’31, a retired professor and one of the university’s first hockey coaches.
“The UW gave me the opportunity to explore and reinvent myself,” Thomsen says. “I learned resilience and not to feel bad about not having a straight career path.”
Her scientific training and hands-on experience proved a strong foundation for her future career. As a research scientist in Jillian Banfield’s UW–Madison geology and geophysics lab, she went from washing equipment to designing underwater experiments in flooded mine sites in southeastern Wisconsin. Plus, she’d been diving since taking her first scuba class as an undergraduate to satisfy both her curiosity and the UW’s physical education requirement. She expanded her skills on dives around the world and more locally as a Wisconsin Historical Society (WHS) volunteer, leading to her full-time role preserving Wisconsin’s underwater heritage.
Today, she leads the WHS Maritime Preservation and Archaeology Program as a maritime archaeologist. Since 2004, she’s documented more than 100 shipwrecks across the Great Lakes, helping secure National Register of Historic Places status for more than 80 sites. She also helps build support for maritime preservation and shares that work through exhibits, media, and educational programming.
Thomsen still loves recreational diving and was enjoying a rare stretch of clear water in usually murky Lake Mendota in spring 2021 when she and her dive partner spotted an exposed piece of wood. She knew almost immediately it was a dugout canoe. That discovery grew into an ongoing archaeological investigation, with subsequent dives revealing at least 16 canoes dating from roughly 700 to more than 5,000 years ago.
“The partnership and collaboration with Native nations is especially integral, and it’s such an honor to be able to help share this history,” Thomsen says. “I’ve worked on hundreds of archaeological sites, and nothing has felt as important as this.”