MICHAEL GRACZYK, Associated Press

ABOARD THE RESEARCH VESSEL MANTA, Gulf of Mexico (AP) — The world will soon get its first good look at the wreckage of the only U.S. Navy ship sunk in combat in the Gulf of Mexico during the Civil War, thanks to sophisticated 3-D sonar images that divers have been collecting this week in the Gulf’s murky depths.

The USS Hatteras, an iron-hulled 210-foot ship that sank about 20 miles off the coast of Galveston, Texas, in January 1863, has sat mostly undisturbed and unnoticed since its wreckage was found in the early 1970s. But recent storm-caused shifts in the seabed where the Hatteras rests 57 feet below the surface have exposed more of it to inspection, and researchers are rushing to get as complete an image of the ship as possible before the sand and silt shifts back.

“You can mark Gettysburg or Manassas, (but) how do you mark a battlefield in the sea?” said Jim Delgado, the director of maritime heritage for the National Oceanic and Atmospheric Administration’s Office of National Marine Sanctuaries, and the person overseeing the project.

On Monday, a team of archaeologists and technicians began two days of scanning the wreckage using a sonar imaging technology that hadn’t been used yet at sea, Delgado said. On Monday aboard the research vessel, Manta, researcher Christopher Horrell gleefully pored over computer images of the Hatteras’ stern and paddlewheels that had just been transmitted from the seafloor.

“This is what I got into archaeology for. It’s fantastic,” said Horrell, a senior marine archaeologist for the Department of the Interior.

The images, taken by a roughly 2-foot-long cylindrical device deposited near the wreckage, were used to position divers who then used 3-D scanning devices to map the site. The sand and silt-filled water near the seafloor limited the divers’ visibility to 3 to 10 feet, and it makes filming or photographing the wreckage difficult. But it doesn’t affect the sonar technology, which produces images by analyzing sound waves bouncing off of objects, allowing scientists to capture a more complete look at the wreckage.

Delgado said he’s hoping to post the images online for the public by January, in time for the 150th anniversary of the battle. He said he also hopes researchers review them to look for ways to preserve the wreckage.

“Whatever we can do to make it accessible,” Delgado said. “We want to share this with folks and show people history is real.”

The Hatteras wreck is in waters administered by the federal Bureau of Ocean Energy Management and the ship itself still remains property of the U.S. Navy.

According to the Navy Historical Center, the 1,126-ton Hatteras was built in 1861 in Wilmington, Del., as a civilian steamship. Later that year, it was purchased by the Navy, commissioned at the Philadelphia Navy Yard and assigned to join the blockade of the Florida coast to keep vessels from delivering supplies and munitions to the Confederacy. It had an active tour in Florida, raiding Cedar Keys and destroying at least seven schooners and facilities before being transferred to the Gulf.

On Jan. 6, 1863, it joined the fleet commanded by David Farragut, of “Damn the torpedoes” fame, for similar assignments off of Galveston, which was then the most prominent city and port in Texas, which had joined the Confederacy. Five days later, it pursued and tracked down a three-masted ship that identified itself as British, but later opened fire on the Hatteras from 25 to 200 yards away and revealed it was actually the CSS Alabama, a notorious Confederate raider.

Forty-three minutes later, with the Hatteras was burning and taking on water, Cmdr. Homer Blake surrendered, and he and his crew were taken aboard the Alabama as prisoners, eventually winding up in Jamaica. Of the 126-man crew, two were lost and are believed entombed in the wreck, which became the only Union warship sunk by a Confederate raider in the Gulf.

“It’s hard to believe we’re in the middle of a battlefield,” said Ed Cotham, the project historian, who carried with him Monday an original photograph of Blake, a formal portrait showing the officer in his uniform. “It’s the first time he’s returned since January 1863.”