Maratón Acuática San Pedro — 20K

A twenty-kilometer descent along the lower Paraná begins at Vuelta de Obligado. The Maratón Acuática San Pedro — 20K is a long-distance open water swimming marathon held in the waters of the Paraná River at San Pedro, in the province of Buenos Aires, Argentina. Swimmers take to the open river in November, carried along by a steady downstream current that transforms raw endurance into a journey through river channels and delta wetlands. The race traces the natural geography of the waterway, following the contours of the Argentine coastline as the current sweeps past islands and low bluffs.

Maratón Acuática: twenty kilometres downstream to San Pedro

The marathon course covers a total distance of 20,000 meters along the wide sweep of the Paraná River, tracing a linear journey that follows the flow of the current. Swimmers dive in at the historic river pass of Vuelta de Obligado and navigate downstream toward the city, aiming for the finish line positioned directly at the host club's dock. Covering twenty kilometers downstream requires sustained focus and steady sighting across open water, as the river's moving volume pulls you forward between mainland bluffs and delta vegetation. The race is organized and hosted on the waterfront by the Club de Pescadores y Náutico San Pedro, working in coordination with the Club Náutico San Pedro.

Once the swimming concludes, the club hosts a welcoming gathering featuring a traditional post-race lunch and awards ceremony where competitors celebrate finishing the marathon together. For swimmers traveling to San Pedro who want to make the most of their journey, the local calendar allows for back-to-back competition. The companion event Aguas Abiertas San Pedro — Club de Pescadores y Náutico is held by the same club just one day before this 20-kilometer marathon, making it possible to complete both races in a single weekend trip.

The Paraná at San Pedro: river channels, delta islands and Arrecifes

The town of San Pedro sits along the right bank of the Paraná River, positioned at the mouth where the Arrecifes River flows into the main stream. This river confluence defines the local geography, creating a rich and shifting aquatic environment where freshwater channels merge. The surrounding waters encompass the wide open channel of the Paraná River, the calmer interior basin of the San Pedro lagoon, the narrow river corridor at Vuelta de Obligado, and a sprawling maze of Delta islands. The Arrecifes River serves as an important tributary that drains directly into the broader Paraná Delta area. As its current enters the basin, it connects with the extensive network of distributary waterways that branch across the delta, including the Paraná de las Palmas further downstream. For open water swimmers, this expansive river network means swimming through a living waterway where the water moves steadily beneath you and the banks alternate between green islands and mainland shores.

The river's seasons, its sandy bed and a pastry from San Pedro

The flow and depth of the Paraná are greatest in the rainy season, peaking in February and March, and lowest in the dry season, which peaks in October. The bed of the Paraná is sandy sediment shaped by a considerable current, and the river is not known for rock hazards on its bottom. In 2022 the municipality of San Pedro opened a public beach at Vuelta de Obligado, 20 km from the centre of the town. San Pedro lies halfway between Buenos Aires and Rosario, 164 km from the capital and 141 km from Rosario by motorway. The people of San Pedro take pride in their ensaimada, a pastry from Majorca that arrived with the Majorcan community at the start of the 20th century.

Vuelta de Obligado and the naval heritage of the Paraná

Starting a long swim at Vuelta de Obligado places competitors at the heart of one of the most famous river passages in Argentine history. The site of the Battle of Vuelta de Obligado is preserved today as a riverside historical museum. Swimmers stepping into the water at this historic crossing start their journey directly from the shore where that river battle unfolded. The river's naval story continues all the way downstream to the finish area at San Pedro. The Irigoyen ship museum is a notable attraction in the city.

San Pedro's cliff viewpoints and riverfront cantinas

Rising above the shoreline, San Pedro is celebrated for its lush green spaces and quiet river atmosphere. The town features a landscaped waterfront promenade that traces the edge of the river bluffs, offering multiple strategic viewpoints perched high on the cliffs with sweeping panoramic views over the Paraná. From these cliffside paths, spectators and families can look out across the broad expanse of water. The tranquil waters along the riverbank and around the adjacent islands make San Pedro an established destination for fishing. The waterfront promenade itself is considered an ideal spot for shore fishing, while local boat operators run fishing excursions out into the Paraná River and through the quieter channels between the delta islands.

After completing twenty demanding kilometers in the water, swimmers head to the town's riverfront dining spots. Local restaurants such as Costeé del Río and Cantina Náutica are set directly on the riverfront, serving regional cuisine with open views of the flowing river. Sitting on a terrace above the water to enjoy local food and watch the river drift by offers the natural conclusion to a long day of marathon swimming.