|The CSS Alabama (background) battles the USS Hatteras. (Copyright, Tom Freeman)|
The Confederate raider Alabama sank the gunboat about 20 miles off Galveston on Jan. 11, 1863.
|This three-dimensional sonar scan shows a top view of remains of the USS Hatteras. (Credit: NOAA)|
|A diver examines the Hatteras' paddlewheel in September 2012 (Credit: Jesse Cancelmo)|
The survey plots damage to the paddlewheel shaft and damage to engine room machinery.
"The engine room spaces were a dangerous place in the battle," Delgado said. "Cannon fire severed steam lines and filled these spaces with scalding steam. Fires broke out, and yet the crew stayed at their post to keep the ship running and fighting, and in here, two of them paid the ultimate price."
• Watch sonar video of USS Hatteras