PREVIEW

More than a century after it slipped beneath the waves, a 108-year-old submarine wreck has been seen in extraordinary detail for the first time, thanks to a recent deep-sea engineering dive off the coast of San Diego.

The U.S. Navy USS F-1 sub was lost on 17 December 1917 in a peacetime collision that killed 19 crew members. Now, cutting-edge ocean technology and a carefully coordinated mission have brought the vessel back into view, capturing high-resolution images of the wreck lying more than 400 metres below the surface.

The discovery was made during a training and engineering expedition from 24 February to 4 March, led by the Woods Hole Oceanographic Institution (WHOI). Using the human-occupied submersible Alvin and the autonomous underwater vehicle Sentry, researchers surveyed the wreck of the F-1 and a nearby Navy torpedo bomber that crashed in 1950.

“Advanced ocean technology and simple teamwork played a big part in delivering these new images,” said Bruce Strickrott, manager of the Alvin Group at WHOI and the sub’s senior pilot. “Once we identified the wreck and determined it was safe to dive, we were able to capture never-before-seen perspectives of the sub. As a U.S. Navy veteran, it was a profound honour to visit the wreck of the F-1 with our ONR and NHHC colleagues aboard Alvin.”

The work was part of a scheduled training mission for Alvin pilots-in-training, but the team’s time on the seafloor has proven historically significant. Visual surveys were completed with sonar, video, and still photography systems aboard the R/V Atlantis and both submersible vehicles.

“The NDSF provides essential equipment for reaching the deep ocean,” said Lisa Clough, acting division director for the National Science Foundation’s Division of Ocean Sciences. “Although HOV Alvin and AUV Sentry are critical for revealing deep-sea geologic hazards and studying remote ecosystems, they also offer opportunities to train the next generation of scientists and uncover crucial moments from our nation’s history.”

For Brad Krueger, an underwater archaeologist with the Naval History and Heritage Command (NHHC), the dive was a first on several fronts. It was not only his initial trip aboard Alvin but also his first in-person visit to a historical wreck site.

“It was an incredibly exciting and humbling experience to visit these historically significant wrecks and to honour the sacrifice of these brave American Sailors,” he said. “All of us at the NHHC are grateful for this collaboration, which also enabled us to document and assess the condition of the crafts.”

Also aboard Alvin was Rob Sparrock, Program Officer at the Office of Naval Research (ONR) and a fellow Navy veteran. “As a Navy veteran, making this dive - together with another Navy veteran and a Navy historian - was a solemn privilege,” he said. “Lasting nearly eight hours, there was time to contemplate the risks that all mariners, past and present, face. It also reminded me of the importance of these training dives, which leverage the knowledge from past dives, lessons learned and sound engineering.”

After the dives, a remembrance ceremony was held aboard the Atlantis above the wreck. A bell tolled 19 times - once for each sailor lost in the F-1 disaster. “History and archaeology are all about people and we felt it was important to read their names aloud,” said Krueger. “The Navy has a solemn responsibility to ensure the legacies of its lost Sailors are remembered.”

Behind the emotion was a wealth of new data. Sonar from Sentry and Atlantis rendered detailed seafloor maps, while Alvin’s high-resolution cameras captured imagery later used to create intricate 3D photogrammetric models. These not only reconstruct the submarine visually but also allow precise measurements of the site and the marine life now inhabiting it.

Anna Michel, chief scientist at the National Deep Submergence Facility and co-lead on the mission, highlighted the significance of the approach. “While these depths were well within the dive capability for Alvin and Sentry, they were technical dives requiring specialised expertise and equipment,” she said. “We were careful and methodical in surveying these historical sites so that we could share these stunning images, while also maintaining the reverence these sites deserve.”