Isla de Lobos sits offshore from Punta del Este, visible from the coast but far enough out to feel like a separate piece of the Atlantic. The island is best known for its sea lions and fur seals, whose noisy colonies are the reason most travellers make the boat trip.
Landings are restricted, so the experience is usually from the water: spray, wind, the lighthouse, and animals covering the rocks. Go in decent weather and with realistic expectations; this is a wildlife excursion, not a beach island.