Dois Rios.

Praia de Dois Rios stretches 1,200 metres along the ocean side of Ilha Grande's south coast, a sand arc closed by rivers at both ends and backed by the village that held the Cândido Mendes penitentiary until 1994, now a UERJ research station. It is one of six beaches on the island's ocean coast where surfing is practiced, and the only one documented by published science instead of surf media: university monitoring measured a wide surf zone where waves arrive preferentially from the east and southeast, breaking as spilling and plunging peaks that shift along the low-gradient bar. Average breaker heights ran from half a metre in summer to 1.7 metres in winter on periods up to fourteen seconds, so the season logic is simple: winter groundswell more than triples the summer baseline. Size is not even along the arc. The southern corner sits behind a rock headland that intercepts part of the south and southwest storm swell, while the northeast end takes the most energy: storm waves there are documented reaching the vegetation line. Getting in is the filter. The T14 trail runs about 9 kilometres from Abraão, better than two hours on foot, or you arrive by boat, and the village keeps 8am to 5pm visiting hours with no camping or overnight stays. Lopes Mendes and Aventureiro carry the island's surf reputation; nobody carries this one, and the lineup is as empty as that suggests.

East swell peels into a kilometre of empty sand below a demolished prison, two hours on foot from the nearest surfer.