Librarians tempted to submerge at the sight of another sub title should keep their periscopes poised for this fast-moving account of submarine exploits from the Confederate Hunley--the first sub to sink a ship--to the Trieste and into the future. The author has researched his subject well, and he comes up with a number of early craft that never came up, as well as the few that did. Submarines were still regarded with skepticism at the start of World War I, but the feat of a German U-boat in sinking three capital ships within two months of the beginning of hostilities, and their successful forays against merchant shipping, forced the Allies into countermeasures, and ultimately forced the United States to enter the war. Here, as in his coverage of engagements during the Second World War, Mr. Widder brings the action into focus by citing first-hand reports and the audacious achievements of individuals. In the post-war period, the reader goes down under the sea in the nuclear-powered Nautilus, the tragic Thresher and the bathyscaphe Trieste--with the promise of more marvels to come. Substantial--but slides down easily.