Reuters: An undated video grab taken from the documentary film Thirty Million shows a riverbank eroding as the rivers of Bangladesh flow into the Bay of Bengal. Raw Cinematics Production/Handout via Reuters left1 of 3right An undated video grab taken from the documentary film Thirty Million shows a young child bathing in muddy waters on Hatiya Island, Bangladesh. Raw Cinematics Production/Handout via Reuters left2 of 3right An undated video grab taken from the documentary film Thirty Million shows an...