The municipality consists of two non-contiguous parts, separated by Carling Township and the Parry Sound. The northern part includes the village of Pointe au Baril on the mainland and most of the geographic townships of Shawanaga and Harrison. This covers the islands and shoreline of Georgian Bay from the Twin Sisters (at the northern boundary of Carling Township) north to Charles Inlet and the Naiscoot River, a few miles south of Britt. The southern part consists of the geographic townships of Cowper and Conger that includes the islands and shoreline of Georgian Bay southwest of Parry Sound, from Twelve Mile Bay (at the Muskoka District boundary) to Parry Island and up the South Channel almost to the Town of Parry Sound. Almost a third of the population of the southern part lives on the islands in the Sans Souci and Copperhead area, centred on Frying Pan Island.
The township is characterized by numerous islands (hence its name) and bays that attract large amounts of vacationers and boaters in the summer. Much of its area is undeveloped and crown-owned land: in the north, 96 percent of the mainland and 50 percent of the islands remain in the public domain, and in the south, 83 percent of the mainland and 70 percent of the islands, a large part of it protected in the The Massasauga Provincial Park.