Submerged Island Off Florida Reveals Secret: Civil War-Era Cemetery

Further research revealed that Mr. Greer had worked as a laborer at the fort, and that the slab on his grave was made from greywacke, the same material used in its construction. He never picked up his final paycheck, nor is there any record of him having been in the hospital, suggesting he may have died a somewhat sudden, violent, death. Dozens of other people were interred at the cemetery, according to historical documents, which also showed that the quarantine hospital had been used to treat yellow fever patients between 1890 and 1900.

For now, the archaeologists plan to leave Mr. Greer’s grave undisturbed. Nor will they reveal the exact location of the site, as is common practice.

“In the Florida Keys, we’re in the birthplace of modern treasure hunting. If you find it in the water, it’s finders keepers,” Mr. Marano said, adding that the role of the National Park Service was to preserve and protect cultural resources. “A lot of times we want to leave it in place,” he added, “because it’s going to be better protected.”

Kirstin Meyer-Kaiser, a marine biologist at the Woods Hole Oceanographic Institution, who was not involved in the survey but has studied the connection between underwater sites and marine biodiversity, said that leaving human artifacts in place was also likely better for any marine wildlife. “It was not supposed to be there in the first place,” she said of the relics. “But after a certain amount of time, any man-made object turns into a habitat.”

Dr. Van Tilburg, the NOAA archaeologist, said that his field was just beginning to comprehend the impacts of climate change on the cultural heritage of the marine environment, but that those in shallow environments, like the Dry Tortugas site, were likely to be the most at risk from storms and other ocean changes. Still, he said, where possible, the gold standard was to leave things where they are.

“Things that are submerged,” he said, “have a story to tell.”