Clive Cussler in between authoring a plethora of novels, book tours and signings finds the time explore shipwrecks and other items of historical significance. Cussler and his NUMA (National Underwater Marine Agency) scour the world to try to unearth clues to unravel some of the mysteries of history. In each chapter he concocts a vignette explaining the history surrounding what he is searching for. He then describes the efforts of his team to uncover the ship or whatever they're going after. They aren't always successful.
As opposed to his first Sea Hunters novel his team has searched for many things other than sunken ships. He spent time in Maine searching for L'Oiseau Blanc, thought to be the first plane to fly non stop across the Atlantic prior to Lindbergh. The NUMA team also tried to uncover the remains of the U.S.S. Akron, the first enormously sized Goodyear blimp which crashed of of the Jersey shore in the 30's.
Of particular interest was learning the fate of the R.M.S. Carpathia, which was responsible for rescuing the survivors of the Titanic, and was subsequently torpedoed by a German U boat 6 years later. A very interesting chapter was devoted to the fate of the Mary Celeste, an extremely famous "ghost" ship of the 1870's. The most revealing discovery for me, surrounded the story of the steamship General Slocum which was involved in the greatest tragedy concerning loss of life in New York history. In excess of 1000 people died as the ship was ravaged by fire on a weekend excursion in New York Harbor. The event actually altered the dynamics of the German American community which inhabited lower Manhattan and suffered huge losses in the fire. They moved away to divorce themselves from the devastation on the General Slocum.