Pine Island Sound is located in Lee County, Florida, lying between Pine Island and the barrier islands of Sanibel Island, Captiva Island, North Captiva Island and Cayo Costa, which separate the Sound from the Gulf of Mexico. The Sound connects to Gasparilla Sound and Charlotte Harbor to the north, and to San Carlos Bay and the Caloosahatchee River to the south. The Sound is conterminous with the Pine Island Sound Aquatic Preserve, which was established in 1970 and consists of 54,000 acres (220 km²) of submerged land.