Doug Miller KHOU

On the floor of the Gulf of Mexico sits a Nazi ship of ghosts, a sunken U-boat whose 52 crewmen died under almost a mile of water just south of the mouth of the Mississippi River.

Depth charges dropped by a Coast Guard escort vessel blasted U-166 apart shortly after it had sunk the SS Robert E. Lee, a freighter that was bound for New Orleans when it was struck by a torpedo late one night in July 1942. Among the 25 dead was a passenger who had survived another U-boat attack.

Over the last few days, the ghostly remnants of both doomed ships have been visited and extensively photographed by a crew of underwater explorers led by the man who discovered the Titanic.

"Everyone thought the war was fought over there, as they would say," said Dr. Bob Ballard, the president of the Ocean Exploration Trust, speaking aboard the exploration vessel Nautilus. "But Hitler brought the war to our doorstep."

Nazi propaganda films trumpeted the triumph of Hitler's U-boats, which sank almost 2,800 allied ships, 549 of them American, most infamously in the north Atlantic. But in the early months after the U.S. entered World War II, the German navy dispatched 22 U-boats to menace shipping in the Gulf of Mexico, including the Texas coastline. Yet few Americans today realize how close the war came to the Gulf Coast.

"And there's a very good reason," said Richie Kohler, a renowned diver and shipwreck historian participating in the expedition. "The United States government didn't want us to know. They didn't want us to know how Germany was taking us to task, how successful these U-boats were."

Operation Drumbeat, as the Nazis called their campaign along the U.S. coastline, was strikingly successful in the Gulf. Historians have counted 56 ships believed to have been sunk by U-boats in the Gulf of Mexico. Americans managed to sink only one U-boat in the Gulf.

Robot cameras dispatched by the Nautilus last week showed the distinctive outline of U-166's conning tower and deck gun, a sight instantly recognizable even to amateur historians and World War II movie buffs. The once sinister ship now sits peacefully on the ocean floor, covered with colorful marine life.

The shipwreck remains have withstood the decades startlingly well. Images beamed back from the sunken remains of the Alcoa Puritan, a vessel struck about 50 miles south of the mouth of the Mississippi River, looked so sharp and clear cameras captured the letters spelling out the ship's name on its bow.

"We were able to go in and literally read the manufacturers label off of some of the machinery," Ballard said. "I was hoping it would be as spectacular as it has been in the past (at other shipwreck sites), and it did not disappoint us."

Watching the video streaming live from the wreck site, Kohler recounted the story of the ship's sinking and the U-boat captain's act of mercy: Firing a torpedo that missed its target, then giving the doomed vessel's crew time to abandon ship.

"We got a U-Boat firing its deck gun and circling this ship until he stopped, then allowing the crew to safely get off, then giving it the coup de gras with a second torpedo," Kohler said.

The high-resolution video shot by the Nautilus will appear in a number of television documentaries that the crew hopes will bring public attention to an aspect of World War II unknown to most contemporary Americans.

'It is a static time capsule," Kohler said. "All of these shipwrecks in deep water are just that. They're moments frozen in time, in history."