Day three of the Paraguay River Expedition, from Porto Santa Anita downstream to just below Bahía Negra, Alto Paraguay, Paraguay, 31 August 2026. A water sample at the confluence of the Paraguay and the Río Negro, then upriver to Tres Gigantes Biological Station—Guyra Paraguay's reserve in the Paraguayan Pantanal, named for the giant otter, giant anteater and giant armadillo—to meet park rangers Lourdes Matozo and Alexis Arias. Giant otters (Pteronura brasiliensis) on the water, a second sample on the way back down the Río Negro, a swim to cool off, and a tropical shower that cleared into a rainbow. The Jaguar Rivers Initiative is an alliance of Rewilding Argentina, Fundación Moisés Bertoni (Paraguay), Nativa (Bolivia) and Onçafari (Brazil). Expedition team: Natalia Rodríguez, Yamila Barasch, Sofía Heinonen, Sebastián Navajas, Paola Bocardo, Stephanie Simioni, and Henry Maillet.