Part of Puerto Rico's national park system, Sun Bay is a long half-moon-shaped bay, less than a half-mile east of Esperanza. It's the island’s balneario (public beach), with all the amenities you could hope for, including lifeguards and a cafe (11am to 5pm daily) serving up criollo treats. Measuring a mile in length, Sun Bay rarely seems busy – even with 100 people sunning and playing on it, it will still appear almost deserted. The surf is gentle.
Head to the eastern end for shady parking places amid the palms and few other sunbathers. For even more solitude, keep heading east on the beach road to Playas Media Luna & Navio. In the evening, kayak companies often begin their tours in the parking lot, taking Sun Bay's dirt roads to access Bahía Mosquito.