Gorriti Island lies a 10-minute boat ride from the Punta del Este port, squarely in the bay. It is only about a kilometre long and easy to cross on foot in half an hour, but it has two sheltered beaches, good snorkelling in the rocks around the perimeter, and the remains of two Spanish colonial fortifications — the Santa Teresa and San Fernando batteries — that were built in the 18th century to control the mouth of the Río de la Plata. The stonework is largely intact, which gives the island an unexpectedly historical feel for somewhere so close to a fashionable resort.
In peak summer season the island fills up with day-trippers and beach parties. In the shoulder months it is much quieter and more pleasant. Small boats run regularly from the port through the summer; out of season you may need to hire a private water taxi. There are no permanent facilities beyond a seasonal food stall; bring water and shade.