Updated

A team spearheaded by the deep-sea explorer who found the Titanic has been searching a little-known ship graveyard located in the Gulf of Mexico that includes the only known Nazi U-boat to have sunk in the Gulf of Mexico during WWII and a few of its targets, MyFoxTampaBay.com reported.

"Hitler brought the war to our doorstep shortly after they declared war on us," Dr. Robert Ballard, the team leader, told The Tampa Bay Times.

His team is spending the month exploring the wreck of a U-boat that sunk the passenger steamer, SS Robert E. Lee, and a few other Nazis targets in the Gulf.

Tom Czekanski, the National WWII Museum curator, told The Times that during the war "America really was under siege."

"Over 20 U-boats operated in the Gulf of Mexico in 1942 and 1943," he told the paper. These U-boats would prowl for American ships at the time.

The U-boat discovered, U-166, sank three small ships and the SS Robert E. Lee south of Louisiana on June 30, 1942, killing 25, MyFoxTampaBay.com reported. A U.S. Navy vessel escorting the SS Lee responded, however, dropping depth charges that crippled the submarine, which eventually sank, killing the 52 on board.

The wreckage of both ships was found back in 2001, about 5,000 feet below the surface of the water, the report said.

"Many souls were lost on these wrecks and others, but now they are teeming with corals and undersea creatures. It's the amazing tapestry of life," Ballard told The Houston Chronicle in an email from on board the Nautilus.

The Ocean Exploration Trust has been transmitting photos and even live video of their explorations from aboard the exploratory vessel. The area is considered a war grave and cannot be disturbed, but the Ocean Exploration Trust team is conducting high resolution mapping in addition to visual surveys to create 3-D images of the wreck sites for further study.