A group of volunteer scuba divers called "Clean Malaren" have been cleaning up Stockholm's canals for the past two years.

They have found 12,000 kilograms of lead batteries, 320 scooters, one car and 30,000 kilograms of other waste on the bottom of the Swedish city's waterways.

"It's a bit contradictory that you are looking at Stockholm from above and you think it's really, really clean," Rasmus Rodineliussen, a volunteer scuba diver, told AFP.

"And compared with a lot of places it is clean, but you still find all this stuff on the bottom and that's an issue if you don't want to acknowledge that."

Video editing: Steve Chappell