Playa Sirena is the headline beach of Cayo Largo — two kilometres of impossibly white sand on the western tip of the island, with shallow turquoise water and almost no development on the beach itself. There is a single restaurant-bar, sunbeds for hire, and lifeguards. Everything else is sand, sea, and the line of mangroves behind.
It is reached by catamaran from the marina on the south coast — a short, scenic crossing. Most resort guests come for the day on an organised excursion. Stay until late afternoon and the crowds thin out completely; the light on the sand and water at that hour is the reason people remember the place.