Dog Island is a 900-acre property that was once part of the relic landmass of the original Colorado River Delta. The island is separated from the mainland by the Gulf Intracoastal Waterway and is located adjacent to the Texas Parks and Wildlife Dept. Mad Island Marsh WMA. It is accessed via a short boat ride from Matagorda harbor. The island's habitats include wooded uplands, tidal wetlands, fringing oyster reef and a small freshwater lake.