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. Important habitats in the Sound include mangroves, seagrasses, salt marshes, oyster communities, tidal flats and sponge beds. All animals in and around Pine Island sound, including mollusks, fish, birds and mammals, are affected by periodic outbreaks of red tide. The Sound is relatively shallow in many locations, and boaters are cautioned to utilize up-to-date charts and tide tables.