The Ortoire River forms the northern boundary between Nariva County and Mayaro County in east Trinidad and the river mouth is located at the southern end of Manzanilla Bay where it empties into the Atlantic Ocean. Other access points to the river include the fish market where the river meets the Manzanilla Mayaro Road and along the bridge on this same road on the outskirts of Mayaro.
It is green in color, however during the raining season it appears brown due to sediment in the water. It is one of the longest and widest streams on the island, running 50km and was previously used by ships to transport goods around the island. This river is home to manatees and has many mangroves along its banks.