In August 2025, the Thunder Bay National Marine Sanctuary dive unit joined forces with experts from the NOAA Diving Program and NOAA Diving Center to conduct a series of deep-water archaeological surveys. Over an intensive three-week expedition, the team executed more than 120 dives to survey nine historic shipwrecks resting in the deep, cold waters of Lake Huron. These sites, ranging in depth from 60 to 100 meters (roughly 200 to 330 feet), represent a significant technical challenge that required the team to look beyond standard scuba equipment.

To document these deep-water sites, the team utilized specialized closed-circuit rebreathers. Unlike traditional scuba systems that provide a finite air supply from a tank, rebreathers use a chemical “scrubber” to remove carbon dioxide while continuously injecting oxygen and inert gases to maintain a safe breathing mixture. This sophisticated configuration allows divers to “recycle” their air, vastly increasing their potential dive time and safety at extreme depths. While these systems require extensive training to master, they are essential for reaching the deepest sites in the sanctuary.

The primary mission of these dives was the collection of high-resolution photogrammetric data to develop scaled, georectified 3D models of the shipwreck sites. These models are a key strategy utilized to support the sanctuary’s management and pr

eservation strategy. By creating 3D models of the same sites over multiple years, researchers can utilize this longitudinal data to precisely track site changes caused by environmental factors or human impact over time.

Beyond their scientific value, these models are transformative tools for public outreach. Because these deep-water wrecks are inaccessible to most, the sanctuary provides a digital bridge through its Sketchfab page, where anyone can virtually explore the Great Lakes’ underwater history. From virtual reality simulations to 3D printing, these datasets ensure that the mysteries of “Shipwreck Alley” are shared with the world. We are grateful for the specialized diving expertise that made this 2025 mission possible and look forward to sharing more results from this landmark project