Hoyo Azul is a natural cenote — a limestone sinkhole filled with groundwater — located within the Cap Cana resort complex near the southern end of the Punta Cana coast. The water is an vivid, almost artificial-looking turquoise, fed by underground springs and surrounded by a 40-metre cliff draped in tropical vegetation.
You reach it by a short trail through dry forest; the setting is dramatic enough to feel genuinely surprising inside what is otherwise a constructed resort environment. Swimming is permitted and the water is deep and clear. It is managed as a tourist attraction by the Cap Cana resort, so access requires a fee and is via guided tour or combined ticket with other Cap Cana activities. Arrive early to beat the resort guests.