Time Out says
Fun fact: the Kallang River is the longest river in Singapore. It stretches for 10 kilometres from the Lower Pierce Reservoir to the Kallang Basin. Before making a name for itself as the top spot for water sports, it used to be home to the sea nomads who lived on boats in the Kallang Basin and pledged allegiance to Temenggong Abdul Rahman of the Johor-Riau Sultanate. Today, you'll find canoes and dragon-boats instead.