Shelter Island is nestled between the North and South Forks of Long Island. The island is surrounded on three sides by Shelter Island Sound. The fourth side, on the east, is adjacent to Gardiners Bay. It can be reached via ferry from Greenport to the north (approximately 8-minute trip) or from North Haven to the south (approximately 5-minute trip). New York State Route 114 runs through the island.
The island is around 8,000 acres in size. However, vast tracts are protected wetlands nature preserve marshland. Nearly one-third of the island is owned by The Nature Conservancy and kept in a forever-wild state. The Preserve has four nature and bird-watching trails, varying in length from 1.5 miles to 11 miles, as well as a barrier-free Braille trail for the visually impaired.