Urban Runoff & Wastewater Treatment In Tokyo Courtesy of Yahoo! News, Odaiba Marine Park, Tokyo Bay, Japan. After the recently held Tokyo 2020 Marathon Swimming Test Event in Odaiba Marine Park was shortened from 10 km to 5 km and its start was moved up to 7:00 am as a precautionary measure against the 29°C - 30°C water, the swim leg of the test event