By Flora Graham - New Scientist
Looking like the weathered skeleton of some ancient dinosaur, the rusting remains of an American Civil War battleship have been imaged in their underwater grave by 3D sonar.
The USS Hatteras sank during battle with the CSS Alabama in 1863, coming to rest in 17 metres of water in the Gulf of Mexico, 30 kilometres off the coast of Galveston, Texas.
One hundred and fifty years later, the bones of the iron-hulled paddle-wheel steamship have been mapped by the US National Oceanic and Atmospheric Administration (NOAA).
NOAA made the scans after local underwater photographer Jesse Cancelmo noticed that recent storms had shifted some of the sediment and sand that covered the wreck.
The main image above shows the curved tooth-like outline of the stern on the right.
The paddle-wheel shaft stretches from the top to the bottom of the picture, where the remains of the port paddle wheel lie crumpled like the bones of a skeletal hand.
More than half of the ship still lies beneath the seabed."
Most shipwreck survey maps are two-dimensional and based on observations made by sight, photographs or by feeling around in murky water while stretching a measuring tape," said James Delgado of NOAA's Office of National Marine Sanctuaries.