Sandy Island contains about 250 hectares. While Sandy Island has seen cottage development only since the late 1970s, the Martyr Islands were first inhabited in 1885.
Sandy Island is a unique environmental area of Georgian Bay.
It is a haven for the Massasauga rattlesnake which finds many comfortable habitats in the low-lying, damp areas throughout the island. The fish sanctuary that is still marked on the small craft charts emerged from a concern about the dwindling bass population in the 1940s. But when this did not happen, because young bass do not move very far from the spawning areas, the sanctuary was finally rescinded. The Isle au Sable name was used from at least the early 1800s to the 1870s. Following the 1870s, the Isle au Sable band became known as the Wasauksing band, which now resides on Parry Island.