A drone might have just uncovered a buried Civil War sub sought for decades

A black drone whirred into the sky over the Rancocas Creek with four cables underneath, clutching a cigar-shaped magnetometer like the prize in an arcade claw game.

From a height of 100 feet, the drone swept over the creek in a zigzag pattern as the magnetometer scanned the landscape for iron — a potential sign that the elusive Alligator Jr., a Union-side Civil War-era submarine prototype, might be buried below.

Watching intently was Alice Smith, who has pursued Alligator Jr. for two decades along the Riverside-Delanco border in Burlington County. Her research indicated the sub had been abandoned or sunk in 1861 somewhere along the creek, which empties into the Delaware River. The drone was the local historian’s last chance. If results were negative, she planned to call it quits at the age of 76.

» READ MORE: For 20 years she’s tried to solve a Civil War mystery in NJ. Now she has a big clue.

Now, she has real hope.

A report released last week by the engineering firm that conducted the drone survey indicates that a large magnetic anomaly weighing from two to 10 tons rests under the mud. The outline is roughly what would be expected of the iron-hulled sub, and in the believed location. However, more work needs to be done to confirm it is indeed Alligator Jr.

“It’s been a 20-year adventure, and extremely enjoyable,” said Smith, the retired president of the Riverside Historical Society, who lives in Delran. “I’d like to accept congratulations, but I think we’re at a point where there are some additional steps to take and I have some mixed emotions. Still, this is probably the best report that I’ve gotten in those 20 years.”

She was hoping for conclusive results, but more work is needed to make a definitive claim that Alligator Jr. has been found. If it is verified, maritime experts say, it would be a significant archaeological and historical find.

Alligator Jr., so dubbed by researchers, served as a prototype for the U.S.’s first naval submarine, the 40-foot-long Alligator, which sank in 1863 off the coast of Cape Hatteras, N.C., and has never been never found.

Smith has assembled an impressive list of volunteer help in her quest for Alligator Jr., which was designed and built in 1859 by French-born inventor Brutus de Villeroi. The vessel was possibly 30 feet long, and weighed at least several tons. The crew likely pedaled, as if on a recumbent bike, to turn the propeller.

The iron-hulled Alligator Jr. was originally built for salvage work, but de Villeroi offered her to the Navy not long after Fort Sumter was fired on, according to the nonprofit Navy & Marine Living History Association. It was bound for testing at the Philadelphia Navy Base when harbor police in Delaware thought the vessel seemed suspicious and seized it in 1861. Thousands gathered for a peek inside the “infernal machine,” according to an account on the Navy & Marine Living History Association website.

The vessel marked the first step toward creation of a modern submarine fleet and had been stored at the Philadelphia Navy Base and Marcus Hook, according to government records and newspapers. It was last thought de Villeroi eventually tied her up along his workshop on the South Jersey side of the Delaware, either forgotten or deliberately sunk in the mud.

Various expeditions and methods over the years had failed to turn up solidly positive results for Alligator Jr. — that is, until the drone and magnetometer combination flew over the area on Sept. 11. Smith is keeping the location secret for now. But the anomaly was detected in an area where children playing on a rope swing reported seeing a metal object in the mud decades ago.

Smith raised funds online to hire RETTEW, an engineering firm with a large magnetometer. Timothy Dunham and Oleksander Kerod, both of RETTEW, who operated and monitored the drone, explained that the magnetometer acts like a big metal detector that measures Earth’s magnetic field. Data from the four flights were uploaded and analyzed by geophysicists at RETTEW to create a topographical map highlighting where metals were detected and in what density.

About 15 friends, family, and volunteers who helped Smith over the years gathered to watch the drone search over wetlands rimmed by Japanese knotweed. Kelly Drumm, Smith’s daughter, was among them. She was in her 20s when her mother started her quest. Drumm is now 48.

“She’s very excited. She’s put so much hard work into this,” Drumm said of her mother. “I don’t think a lot of people really understand the extent of the research she’s conducted. She’s just so passionate about it.”

Steve Nagiewicz, an adjunct faculty member of Marine Science at Stockton University, was also on hand. Nagiewicz is a divemaster and specializes in remote sensing technology and marine archaeology.

Vince Capone, founder of Black Laser Learning, a sonar technology company, has helped Smith for years and has decades of experience locating shipwrecks.

“There is a very good indication there’s a mass of iron in the marsh, and the area roughly corresponds to some of the evidence that Alice has put together,” Capone said of the magnetometer search. “But it is not conclusive that it is the submarine.”

Capone said ground-penetrating radar is needed to get a clearer picture of what’s there. Researchers would then need to dig a test hole.

Capone is doubtful a drain pipe, boat engine, or some other detritus would give off such a strong signal from 100 feet in the air. If it does prove to be the submarine, excavating it could be a complex and expensive undertaking, Capone said. Researchers would need archaeological and environmental permits.

For now, Capone said, it’s important to keep the location secret. He’s written a report on the findings with GPS coordinates redacted. It would be dangerous for amateurs to venture into the area, he said.

James Delgado, a preeminent U.S. maritime archaeologist, said verification of Alligator Jr. would be “not only historically significant, but archaeologically significant.”

Delgado was director of the Maritime Heritage Program for the National Park Service, helmed a shipwreck program for the National Oceanic and Atmospheric Administration, and wrote guidelines for putting ships and shipwrecks on the National Register of Historic Places. He is currently a senior vice president with SEARCH, which bills itself as “a global leader in archaeology, maritime archaeology.”

Delgado said Alligator Jr. was developed during an intensely competitive time as 19th-century inventors from around the world raced to patent submarine technology.

“There’s not that many of these things left around,” Delgado said. “There were so many being made, but how many survived? Very few. I mean, there’s just a handful.”

He thinks that if the anomaly is confirmed as Alligator Jr., it could be a candidate for the National Register of Historic Places, and that Smith should get credit.

“Alice is in many ways the hero of this because it’s her knowledge and her perseverance that has inspired others to step up.”