LAKE MEAD, AZ (3TV/CBS5) - It wasn't the crash or the splash in 1948. It wasn't the 70 years of exposure to the lake's frigid waters. It wasn't the 20 year drought that lowered water levels by more than 100 feet and the algae that followed, or even the scavenger divers who stole relics from the aircraft.

None of those acts of man or nature have threatened the survival of the Lake Mead B-29 quite like the quagga mussels that now cover the fuselage.

[WATCH: WWII bomber crash site under Lake Mead's water]

In the summer of 1948, the US military was using the B-29 for a secret mission, testing new equipment, when the plane skimmed the surface of Lake Mead and sank. The pilot and crew escaped relatively unscathed. But because of the secret nature of the mission, the location of the wreckage remained unknown until 2001.

[RELATED: 7 states seek US support for Colorado River drought plan]

"There was always a rumor that there was this plane at the bottom of Lake Mead," said Joel Silverstein, who is the vice president of Tech Diving Limited, and one of the few divers who has seen the wreck in person.

"When I first dived, it was close to 200 foot depth. And you come upon the tail of it and it just starts to loom out of the darkness and all of a sudden you start to see the entire shape of the plane there. And there’s this moment of pause when you think how did that get here?" said Silverstein.

The National Park Service has allowed Silverstein to take a limited number of divers to the wreck in the past, but the site is off limits today, and will likely remain that way through at least the end of this year.

The quaggas arrived in Lake Mead around 2004. They are an invasive species  of mussel that likely arrived in the bilge of visiting boats. They now cover the B-29.

"Right now we calculated that there’s about two tons of quagga mussels laying over all of the surface of the B-29," said Silverstein. "They’re damaging the plane from their massive weight," he said.

At this point, there is no plan in place to deal with the invasive mussels. But Silverstein, who has dived wrecks all over the world, says it's worth the investment to protect this one.

"The significance of this plane is that there are only a few B-29s left. It is the only one that is intact underwater, so it is a cultural resource. It’s important that it stay preserved and stay protected," said Silverstein.

[SPECIAL SECTION: CBS 5 Investigates]

Morgan Loew's hard-hitting investigations can be seen weekdays on CBS 5 News at 6:30 p.m. and 10 p.m.

Copyright 2019 KPHO/KTVK (KPHO Broadcasting Corporation). All rights reserved.

Recommended for you