Devil' Gate by Clive Cussler

Clive Cussler, adventurer and author, leads an exciting life of exploration: "Clive Cussler began writing in 1965 and published his first novel featuring Dirk Pitt® in 1973. His first non-fiction work, The Sea Hunters, was released in 1996.
Clive is the founder of the National Underwater & Marine Agency, (NUMA) a non-profit organisation that dedicates itself to American maritime and naval history. Cussler and his crew of marine experts and NUMA volunteers have discovered over 60 historically significant underwater wreck sites. After verifying their finds, NUMA turns the rights to the artifacts over to non-profits, universities, or government entities all over the world. Some of these finds include the C.S.S. Hunley, best known as the first submarine to sink a ship in battle and the U-20, the U-boat that sank the Lusitania. (from the Clive Cussler website.)
Clive Cussler's latest book, Devil's Gate is ninth in the Numa Files series featuring Kurt Austin.