Storms and floods are causing almost 200 sunken wooden war vessels to move.
The underwater skeletons of 185 wooden ships, referred to as ghost vessels, were deliberately sunk or have been left to decompose for hundreds of years.
Over time, the wrecks, which include ships from the Revolutionary War and Civil War, have transformed an area of the Potomac River, called Mallows Bay, into a vibrant ecosystem.
Environmentalists have come to value the ships as a plethora of wildlife make their homes aboard their wooden remains, dense with shrubs and nutrient-rich soil.
The forested cove is home to many species of fish, birds, deer and beaver, among others.
The National Oceanic and Atmospheric Administration (NOAA) previously described the 14-square mile area as ‘one of the most ecologically valuable’ sites in the state of Maryland.
But researchers, accompanied by school children from J.C Parks Elementary School, studied aerial maps of the area, which showed the ships were shifting eastwards, some as far as 20 miles, as reported by Live Science.
Storms, erosion and floods have all caused the vessels to move, and could cause considerable disruption to the vibrant ecosystem.
A further evaluation of the site is going to be undertaken using underwater vehicles to see how the future movement could impact the wildlife in the area.
The rotted fleet is the largest group of historic watercraft visible in the Western Hemisphere.
Don Shomette, a 72-year-old marine archaeologist, collected and analyzed data from the ships, compiling a 500-page dossier documenting in great detail each member of the fleet.
In 2015, he said: ‘It is hard to say what my favorite projects are because all discovery is exciting,’
‘But of course, Mallows Bay is incomparable.’
Joel Dunn, president of the Chesapeake Conservancy, previously said: ‘Each ship has become a mini eco-system.
‘So whether it’s an osprey to build a nest on, a striped bass to survive in or an oyster to cling onto, the ships provide structure for life to survive.’
Dunn’s non-profit organisation is one of the groups pushing for Mallows Bay to be designated a national marine sanctuary, a process that is currently underway.