Laguna Oca is an oxbow lake formed from an abandoned meander of the río Paraguay, located approximately 10 kilometers south of the city of Formosa in northern Argentina. The lagoon sits within the Laguna Oca del Río Paraguay Biosphere Reserve, which covers roughly 10,500 hectares and was designated a UNESCO Biosphere Reserve in September 2001. It is notable for being the first urban biosphere reserve in the world, with no point in the reserve lying far from the city of Formosa.

The surrounding landscape is a floodplain shaped by the río Paraguay, comprising a mosaic of meanders, oxbow lakes, wetlands, gallery forests, palm savannas, and sediment ridges known as albardones. The reserve supports a wide range of wildlife, including capybara, caimans, Neotropical otters, coypus, coatis, howler monkeys, and peccaries. Birdlife is abundant and includes species such as the white-throated ibis, bare-faced curassow, cocoi heron, and jabiru stork. Floating vegetation and water hyacinth are present on the water's surface.

The lagoon has a designated recreational beach area that is open daily from 10:00 to 20:00 and staffed with nautical safety personnel. Kayaks and canoes can be rented to paddle through the lagoon and the surrounding network of channels. Guided tours are available for photography safaris and birdwatching. The Costanera de Formosa waterfront in the city serves as an alternative starting point, from which boat and kayak excursions can enter the reserve through the water channels.

Access by road is via Avenida 9 de Julio heading south from the city center, transitioning to a dirt road that leads to the protected area. Laguna García, a secondary lagoon with viewing platforms and walkways, is passed along the way before reaching the main recreational area at approximately 2.8 kilometers. The dirt road is typically closed after rain to prevent damage, and access at those times is limited to foot, bicycle, or motorbike.

The climate is subtropical and warm. Light clothing suited to high temperatures and insect repellent are recommended. A full day is suggested for paddling the channels and lagoons in depth, though a shorter visit of three to five hours is sufficient for a more limited exploration.