A new golden age of exploring beneath the ocean blue

In the 19th and early 20th centuries, archaeology enjoyed a golden age, as explorers unearthed the tomb of King Tutankhamen in Egypt and pyramid-studded Mayan cities lost in the jungles of Central America.

Now, a century later, archaeology is entering a new golden age, with significant discoveries reported almost monthly. But this time most of the discoveries are taking place underwater.

Throughout human history, boats and ships have been lost at sea, and rising seas have buried ancient cities and harbors under water and silt. In the past decade, technological advances have allowed archaeologists and deep-sea explorers to make remarkable discoveries from the Titanic to entire ancient cities sunk off the coasts of Egypt and India.

Many of these discoveries were possible because of new tools, such as high-resolution sonar, sub-bottom profilers, and agile robotic vehicles. But, as in space exploration, there are some things that are best done in person, particularly the painstaking excavation of an archaeological site.

For the past 25 years, Daniel Lenihan has been involved in the "low-tech" side of underwater exploration. Founder and longtime head of the US government's only underwater archaeological team, Mr. Lenihan has led an elite cadre of scuba divers on far-flung, often dangerous, missions in underwater caves, buildings, and wrecks.

When the Navy needed experts to survey and evaluate the integrity of the USS Arizona, they called Lenihan and his National Park Service Submerged Cultural Resources Unit to Pearl Harbor to do the job. They've been to Bikini Atoll to survey the aircraft carrier Saratoga and other ships sunk in atomic bomb tests there, and into the frigid depths of Lake Superior to map the many ships destroyed by Great Lakes storms.

"At archaeological sites on land, you have to dig through different layers of history and try to separate out when this or that happened," says Lenihan, who describes his frequently harrowing underwater experiences in his new book, "Submerged: The Adventures of America's Most Elite and Extreme Underwater Archeology Team" (Newmarket Press). "But each shipwreck is a frozen snapshot of a particular time in history. They're very powerful archaeological sites."

Lenihan and his colleagues have shown just how much can be learned from the careful scientific excavation of shipwrecks. The artifacts on such a site are like pieces of a complex puzzle that, with care, can tell a great deal about shipboard life, trade, fishing, or military practices at the time.

"Underwater archaeology is a little bit like forensics," he says. "You look for little clues to tell you what happened to the ship or what life was like aboard. But if somebody takes away some of the clues, you may never be able to reconstruct some of the past."

Unfortunately, Lenihan reports that a great deal of the United States' maritime past has been destroyed by unscrupulous treasure hunters.

He has little sympathy for "greed-driven" treasure hunters who destroy "priceless information on the lifeways of seamen" and our maritime past in a "frenzied bottom-clawing" for treasure. Sometimes treasure hunters use prop-wash deflectors to aim the full force of their ship's propellers straight down at a wreck. The wash blows huge holes in the bottom sands and, often, the wreck itself, but expose gold and silver intact.

The wrecks are owned by the American people, but Lenihan reports that politicians and judges often condone their destruction by profit-seeking commercial salvage operations. His team once had less than two weeks to find a British man-of-war in Florida's Biscayne National Park after a judge ruled that treasure hunters could "salvage" the ship inside the park limits. The only way the National Park Service could prevent the destruction of the wreck was to "demonstrate its stewardship" of it by locating it. Lenihan's team was able to do that, and the 300-year-old wreck was protected.

"We've made history a commodity," he says. "When you start selling off your heritage, you damage the real core and fabric of what you are as a people." But Lenihan has helped discover, catalog, and preserve much of America's sunken past.

In Lake Superior, he found 19th-century shipwrecks piled on top of one another, testimony to the region's sudden, violent storms. While examining a Japanese submarine in the Aleutian Islands, Lenihan suddenly realized the "ramp" he was straddling was, in fact, a live torpedo.

At Bikini his team surveyed the bomb-scorched Saratoga and the Japanese battleship Nagato, clearing the way for recreational divers, who now spend thousands of dollars to dive to these cold-war monuments.

Currently the team is examining a ferry that sank at Ellis Island, whence it had transported millions of immigrants to real freedom on the mainland.

While Lenihan is passionate about preserving America's shipwrecks, he's equally passionate about allowing the public to visit them. It was Lenihan's love of scuba diving that led him to study archaeology, rather than the other way around, and he believes properly trained divers should be free to explore wrecks, even dangerous ones.

Lenihan's lifelong advocacy for recreational divers is starting to pay off. Sport diving has grown enormously since Lenihan started surveying wrecks a quarter century ago, building an increasingly important lobby for the preservation of historic shipwrecks. "After a [prop-wash] blower runs over a wreck, you may not want to dive on it," he says. "Sport divers are finding they have a lot more in common with preservationists than treasure salvers."