Award-winning underwater cinematographer Kim Dong-sik is currently documenting the stream's diverse ecosystem Images shared on Instagram show Kim Dong-sik, an underwater cinematographer, in Seoul’s Cheonggye Stream. (Instagram @angelicasong) Tourists strolling along Seoul's Cheonggye Stream recently found themselves distracted by an unusual sight: a man in a black wetsuit gliding through the shallow water beneath the city's busy downtown streets.Videos of the unidentified man with snorkeling gear have recently spread across social media, triggering curiosity about his identity and what he was doing.One tourist who spotted the man while walking along the stream on May 28 posted a video on Instagram, writing, “Is that guy snorkeling? Can someone please explain? Everyone around me is confused.”The post soon filled with guesses about the man. Some users wrote that he was simply indulging in an unusual hobby, while others suggested he might be cleaning the stream or carrying out an ecological survey.The swimmer has been identified by local media as Kim Dong-sik, an award-winning underwater cinematographer, who is currently documenting the stream's ecosystem."Cheonggye Stream is a globally recognized example of successful urban ecological restoration," Kim was quoted as saying by Yonhap News TV on Thursday.He said the stream supports several fish species typically found in clean freshwater habitats, including Korean shiners, sweetfish and pale chubs."My dream is to help preserve this place so future generations can experience the same ecosystem and find comfort in it," he said.Kim, who holds a doctorate in fisheries science, has spent more than four decades filming underwater environments and documenting aquatic life.He is best known for his work on the documentary “Whales and I,” which explores the lives of whales and their relationship to humanity. The film earned him the best artistic director award at the 60th Baeksang Arts Awards, an honor he shared with fellow cinematographer Lim Wan-ho.