The drought that has parched much of the southwest may soon yield a mystery that has rested at the bottom of Nevada's Lake Mead for nearly 70 years, a B-29 bomber that went down carrying a top-secret missile defense system that may have actually caused the crash.

The B-29 bomber, also known as the "Superfortress" and the same model as the storied Enola Gay and Bockscar, the planes that dropped atomic bombs on Japan, crashed in 1948 as it flew over the giant lake testing a sun-powered missile guidance system. For decades, it lay at a depth of 300 feet in the man-made lake that was formed by construction of the Hoover Dam. But the drought has lowered water levels to the point where the plane is just 110 feet down, well within the range of recreational divers.

"There's a lot of history there. The site would be right up there with any shipwreck for a diver."

- Curtis Snaper, Sin City Scuba

"It would be amazing," Curtis Snaper, of Sin City Scuba in nearby Las Vegas, told FoxNews.com. "There's a lot of history there. The site would be right up there with any shipwreck for a diver."

The B-29 at the bottom of Lake Mead was one of the last of its kind to be built. The U.S. Army Air Forces, which would later become the U.S. Air Force, received it days after Japan surrendered, on Sept. 2, 1945. Two years later, the plane was stripped of its defensive armament and was turned over to the military’s Upper Atmosphere Research Project. When it went down on June 21, 1948, the plane and its five-man crew were testing a secret ballistic-missile guidance system known as a "sun-tracker," according to the blog War is Boring. According to the blog, the highly-classified device, mounted in a dorsal dome atop the bomber’s fuselage, allowed a missile to get its elevation and orientation from sighting the sun.

Testing it required the B-29’s crew to repeatedly ascend to 35,000 feet, then drop to just 100 feet above the lake. But, according to the blog, the lake's surface reflected the sun, and may have caused Capt. Robert Madison to lose depth perception. The plane skimmed into the lake at 230 miles per hour, and while the crew escaped on life rafts, the plane dropped to the murky depths.

Better-equipped divers, using a special helium-rich gas mixture, for example, have been secretly exploring the crash site since 2001, when it was first discovered in the giant lake's Overton Arm section. But scuba divers have been officially banned by the National Park Service from exploring the site because of the dangers associated with such depths. With Lake Mead at record low levels, the federal agency intends to grant permits for diving the bomber, beginning in April.

But it was not simply the danger to divers that prompted the Park Service to protect it from mistreatment and to prevent recreational divers from going down to the wreckage site. The agency is also concerned that weekend warriors could damage the wreck. In 2002, it sent a remote-controlled submarine down to explore the wreckage, and discovered ropes and lights from previous dives. A year later, technical divers sent down by the Parks Service found signs of damage and looting.

In 2007, the agency allowed two licensed dive operators to lead guided scuba tours of the site, but demand was limited.

“It was costly to dive,” said Steve Schafer of Lake Mead Technical Dives, which led a handful of tours, charging divers $450 each. “We weren’t even allowed to keep a boat on the water to make things go quickly.”

Plunging water levels have made the site much more accessible, and likely much cheaper, for recreational scuba divers, although they would still have to be accompanied by approved guides. The Parks Service plans to offer a two-year, commercial-use permit allowing guides to take up to 100 divers per year down to the wreck.

“We have had people express an interest over the years," Christie Vanover, a spokesperson for Lake Mead National Recreation Area said to the Las Vegas Review-Journal. We think this is the best option, and it provides a business opportunity.”

Perry Chiaramonte is a reporter for FoxNews.com. Follow him on Twitter at @perrych