The borough of Lachine wants to reopen beaches for swimming that have been closed for nearly half-a-century, and for that to happen, there's a lot of trash to pick up.

Scuba divers were on the bottom of the St. Lawrence River looking for junk Sunday, as part of a 24-hour cleanup operation to scour the riverbed for trash resting on the bottom of the water.

Underwater explorer and filmmaker Nathalie Lasselin led the 60 divers that worked for an entire day and brought up four tons of garbage including stacks of car tires, a gun, a pair of ice skates, a parking meter sign and an entire motorbike.

"Anything you can buy at the stores, you find it in the water," said Lasselin, who specializes diving in harsh conditions. "There's still a car down there that we're going to remove later on just to make sure that the way that we do it is really safe for everybody."

Operation Cleanup 360 will include 10 dives over the next year with the goal of removing 100 tons of waste from the water.

"I knew there was a lot of junk at the bottom," said Lachine Mayor Maja Vodanovic. "Everyone was telling me about it. They said we've seen it, it's dangerous, and now, finally, we're starting to bring it out."

Vodanovic said she would like to see the beaches reopened, but knows the riverbed needs cleaning for that to happen.

"We want to eventually swim here, so this is very important," said Vodanovic.

Jonathan Theoret is the director of GRAME, which works on finding solutions to major environmental problems. He said seeing the amount of waste brought up in just one day suggested the problem is enormous.

"That's only 800 metres of shore," said Theoret. "It's a huge problem. There's many other places to clean up and we have to take care of the quality of our water."

Theoret said the material removed from the river will be recycled where possible, brought to eco-centres and properly disposed of. He said the group plans to plant trees and modify the shoreline to slow the path of trash to the water.

He said that the problem could be solved if citizens found littering unacceptable to begin with.

"It should not be accepted that anybody puts one piece of trash on the floor. With the wind it goes straight into the water, straight into the ocean," said Theoret.

Lasselin got the idea to do a riverbed cleanup when she dove last year from Ile Perot to Repentigny and realized the St. Lawrence River needed attention.

"When you're an explorer, you want to go so far away from home and discover the world, and you come back and on the flight, you just see the St. Lawrence River, and you're like, 'huh. How come I don't know that river," she said. "More specifically, because that river is the source of my tap water you just discovered that this is the most precious thing in your life."

Lasselin said that those who don't go under the water to check things out, don't realize the debris that winds up on the riverbed.

"A lot of people think that. They think if I don't see it, it doesn't exist, so basically people used to dump garbage everywhere," she said. "As a scuba diver, we are witness to everything that is happening underwater, and when you see it, you're like, 'it's not right.' It doesn't make sense that all of the garbage are in the water, so you decide just to clean it."

The ultimate goal is to remove 100 tons of garbage from the riverbed over the next year.