Sheet Harbour is located between the East and West Rivers. These two rivers flow into the harbour. East River is a large, deep water area that leads out to the harbour and the West River is a large, fast flowing river with spectacular falls into the main harbour. 

Sheet Harbour gradually widens as it travels southeastward toward the Atlantic. The harbour has an average tidal range of about 1.2 to 1.5 m (4 to 5 ft).

Sheet Harbour was the first community in North America to use a lime doser on one of its rivers, which sprays limestone into the water to stabilize pH levels. Dosing began in September 2005 in West River. It was successful in stabilizing the pH of the river at 5.5, a healthy level for salmon and other aquatic life.