It is a story by Clive Cussler who uses similar plots in all his Dirk Pitt novels...sometime in the past an event happens which leaves Dirk with a mystery to solve to save the world. This one involves a Civil War ironclad breaking through a blockade and keepin' on goin' across the Atlantic, up a river in Africa and being stranded when the water table shifts leaving it stranded in the ever growing Sahara desert.