More than 100 volunteers are cleaning up Stockholm by pulling harmful waste out of the city's lakes and waterways. When diver and social care worker, Frederik Johansson's friend bought a boat in 2018, he dived under to check the hull. He was shocked to discover how much waste discarded by boat owners littered the Swedish capital's waterways. He decided to do something about it and set up a group of volunteers called Rena Mälaren, meaning "clean lake Mälaren" in Swedish. Their aim is to remove toxins from the lake and the Baltic Sea while encouraging people not to treat these fragile ecosystems as a rubbish dump.