Skeleton Coast. Oregon Files #4, Paperback/Clive Cussler

1896: HMS Rove vanishes in a shocking storm off the African coast. Aboard is a fortune in stolen diamonds... Present day: Juan Cabrillo and the crew of the covert super-ship Oregon have just escaped a double-cross on the Congo River when they come to the aid of Sloane Macintyre - looking for some long lost treasure.