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Beneath the ocean's surface are thousands of miles of death traps, which snare marine life and will likely do so for hundreds of years unless people take the risky dive to clean them up.

"People don't realize what is happening underneath the ocean," said Karim Hamza, who dives to retrieve refuse like abandoned nets that are thrown into the water by fishermen or have sunk with ships. The lost nets contribute to an issue called "ghost fishing."

"Those nets are fishing 24/7. They are killing everything, from fish, crustaceans, mammals, sea lions, dolphins. It is indiscriminate," Hamza said.

An estimated 25,000 nets are discarded annually in the Northeast Atlantic alone, according to World Animal Protection.

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A diver retrieves a discarded net from the ocean. Shingo Ishida / NBC News

Hazma said these nets can weigh up to 10,000 pounds, and diving teams have to take multiple trips just to get 200 to 300 pounds of nets out of the ocean.

Depending on the material of the net, they will trap creatures for anywhere from 40 to 600 years, Hazma said.

Ghost fishing has economic and environmental repercussions.

"Some studies estimate that over 90% of species caught in DFG (derelict fishing gear) are of commercial value," which results in a loss of revenue for fishermen, said a 2015 report from the National Oceanic and Atmospheric Association.

The nets also drag across the ocean floor, destroying habitats like coral reefs, according to NOAA.

"It's a growing problem. It's choking our environment. It doesn't benefit anyone, including the fisherman, because it’s killing their stock, and it’s also a danger to the divers," Hamza said.

He would like to see mandatory reporting rules enforced for fishermen, boat captains and divers who happen to spot the nets so that divers can work to get the nets out of the ocean as quickly as possible. "The fresher the net, the easier it is to remove it from the bottom of the ocean," Hamza said.

NOAA also recommends affordable reception facilities for the nets because fishermen often dump gear into the ocean to avoid high disposal costs.

"We have a beautiful natural resource and we are not taking care of it. We are destroying it," Hazma said. "And people don’t see that because they only see the surface."