On a recent Sunday afternoon, the divers arrived on a thin strip of sand at the furthest, watery edge of New York City. Air tanks strapped to their backs, they waded into the sea and descended into an environment far different from their usual terrestrial surroundings of concrete, traffic and trash-strewn sidewalks.

Horseshoe crabs and other crustaceans crawl on a seabed encrusted with barnacles and colonies of coral. Spiny-finned sea robin, blackfish and wayward angelfish swim in the murky ocean tinted green by sheets of algae.

Not all is pretty. Plastic bottles, candy wrappers and miles and miles of fishing line drift with the tides, endangering sea life.

The undersea litter isn鈥檛 always visible from the shore. But it has long been a concern of Nicole Zelek, founder of the dive school SuperDive who four years ago launched monthly cleanups at this small cove in the community of Far Rockaway, where New York City meets the Atlantic Ocean, about 4 miles (6.4 kilometers) south of John F. Kennedy International Airport in Queens.

A throwaway culture of single-use plastics and other hard-to-degrade material has over the decades, posing a danger to marine life such as seals and seabirds.

Dive by dive, small groups like Zelek鈥檚 have been trying to undo some of the damage as part of the DIVERS-ity Inititative, which promotes inclusion in the sport.

鈥淓very month we have a prize for the weirdest find,鈥� she said. They have included the occasional goat skull, perhaps used as part of some ritual, Zelek surmises.

鈥淭he best find of all time was an actual ATM machine. Unfortunately, it was empty,鈥� she said.

The divers鈥� haul one late-summer Sunday wasn鈥檛 much, but there were clumps and clumps of fishing line untangled from underwater objects. What the divers can鈥檛 pull away by hand is cut with scissors.

鈥淯nfortunately, tons of crabs and 鈥� which are under threat 鈥� get tangled in the fishing line and then they die,鈥� Zelek said.

While are underway to scoop up huge accumulations of floating debris in deeper waters, small-scale coastal cleanups like Zelek鈥檚 are an important part of the battle against ocean pollution, said Nick Mallos, vice president of conservation for Ocean Conservancy.

鈥淭he science is very clear and that鈥檚 to tackle our global plastic pollution crisis,鈥� he said. 鈥淲e have to do it all.鈥�

Every September, the conservancy holds monthlong international coastal cleanups. Since its inception nearly four decades ago, the cleanups have retrieved about 400 million pounds (181.4 million kilograms) of trash from coastal areas around the world.

The best way to combat plastics going into the oceans, Mallos said, is to reduce the globe鈥檚 dependence on them, particularly in packaging consumer products. But human-powered cleanup is the least costly of all cleanup options.

By 2025, some 250 million tons (226.7 million metric tons) of plastic will have found its way into the , according to the PADI AWARE Foundation, a conservation group sponsoring a global project called Dive Against Debris.

The project invites what organizers call 鈥渃itizen scientists鈥� to survey their diving sites to help catalog the myriad items that don鈥檛 belong in oceans, lakes and other bodies of water. By the group鈥檚 count, more than 90,000 participants have conducted more than 21,000 such surveys and removed 2.2 million pieces of junk, big and small.

Zelek and her fellow divers have contributed their finds to the project.

Surface trash might be easy enough to clear with a rake, but the task is more challenging beneath the water. Over the years, the layers of monofilament fishing line have accumulated. And until a few years ago, no one was scooping out the line, hooks and lead weights.

Untangled, a pound of medium-weight fishing filament would stretch to a bit more than 4 miles (6.4 kilometers). It鈥檚 anybody鈥檚 guess how many miles of fishing line remain on the channel鈥檚 bottom.

鈥淭hose small things are really what start to accumulate and become a much larger and bigger problem,鈥� said Tanasia Swift, who has been with the group for a year and works for an environmental nonprofit focused on restoring the health of New York City鈥檚 waters.

鈥淚f there鈥檚 anything that we see that doesn鈥檛 belong in the water, we take it out,鈥� she said.

While the drivers work, fishermen cast their lines from a ledge where the city鈥檚 concrete stops. The beach is frequented mostly by residents who live nearby.

Raquel Gonzalez is one such resident, and she鈥檚 been coming to the beach for years. She and a neighbor brought a rake with them on the same Sunday the divers were there.

鈥淣eeds a lot of cleanup here. There鈥檚 nobody that does any cleanup around here. We have to clean it up ourselves,鈥� she said.

鈥淚 love this spot, I love the scuba divers,鈥� Gonzalez said. 鈥淟ook at all the good people here.鈥�