Seven Mile Beach (Grand Cayman)

The short version, from the cited sources

Seven Mile Beach runs along the sheltered western shore of Grand Cayman, a corridor of coral-white sand and glass-clear water that carries most of the island's resorts yet remains public along its entire length by law. The absence of surf, the long gentle shelf and reef snorkelling at either end make it one of the Caribbean's most usable great beaches. Its actual length is closer to nine kilometres than seven miles.