Cruce del Rio de la Plata

The Río de la Plata is defined by its sheer scale and the volatile behavior of the Sudestada, a persistent southeast wind that can force the river level to rise by nearly four meters. When this phenomenon occurs, it brings heavy rains and intense, choppy waves that turn the water into a formidable obstacle for any swimmer. Beyond the wind, the river acts as a massive conveyor of sediment, transporting approximately 160 million tons of silt, clay, and sand annually. This constant deposition forms expansive, shallow sandbanks like the Ortiz and Arquímedes, which demand constant navigation adjustments to avoid grounding or getting caught in unpredictable currents. The estuary also hides a complex salinity gradient; while the inner sections remain fresh, a distinct tongue of lower-salinity water stretches up to 45 km into the sea, shifting the buoyancy beneath you as you progress through the longer distances.

Historical currents and landmarks

Swimming here means moving through a waterway that has seen centuries of conflict and seismic history. Beneath the surface, the sediment-heavy water often obscures the geography, but the presence of the Martín García Island serves as a primary navigational reference. Rising 27 meters above sea level, this rocky outcrop is composed of ancient formations from the Brasilia massif, dating back 1.8 billion years—a stark contrast to the shifting riverbed. History also weighs heavily on the coastline: near the Santo Domingo friary, the ground beneath the 5 de Julio passageway is said to hold a mass grave of British soldiers from the 1807 defense of Buenos Aires. The riverbed itself has even been reshaped by the earth; in 1888, a magnitude 5.5 earthquake with an epicenter 30 meters deep in the river center was felt across both Buenos Aires and Montevideo. While the 1939 Battle of the River Plate took place further offshore, the echoes of naval history remain a part of the local lore. For those preparing for extreme challenges, the ACNRP organizes annual crossings with distances of 40km, 60km, and 100km, a scale that echoes the ambition of the first successful attempts recorded in 1919. If you are looking for shorter, nocturnal efforts to calibrate your night-swimming rhythm, you might find Aguas Abiertas Nocturnas a useful addition to your training schedule.