Argentina created the park on January 13, 1992, under National Law 24.063, setting aside roughly 25 square kilometers to preserve a piece of the Upper Delta. The choice of site was deliberate: this is precisely the zone where the Paraná transitions from a river into a delta. Here the water loses its hurry, drops its load of suspended silt, and the silt becomes ground. New islands form while old channels shift and silt closed. The park belongs to the Paraná Delta and Islands ecoregion, and the wider delta has been recognized internationally as a wetland of significance. To stand at its edge is to watch geography happen in real time, slowly, as it has for millennia.

Few places in Argentina pack in this much life. Capybaras, the world's largest rodents, graze in groups along the waterways, half-submerged and unbothered, while coypu rustle through the reed beds. The riparian forest and open water together support a remarkable range of birds: ringed kingfishers diving for fish, southern screamers calling their harsh two-note alarm from the marsh, herons and storks stalking the shallows, ducks and coots scattered across the lagoons. Beneath the surface the abundance continues, with well over a hundred species of fish moving through the channels, among them the prized surubí catfish and the migratory sábalo that travels the river in vast schools. This profusion is no accident. Deltas are among Earth's most productive ecosystems, places where nutrient-rich sediment, shallow warm water, and endless edges between land and water combine to feed an extraordinary web of life, and the Paraná's delta is among the largest of them all.

There are no roads into the heart of Predelta; the only way in is by water. From the ranger station near Diamante, boats set out into the channels, and canoes and kayaks slip into the narrow arroyos that thread between the islands. The experience is intimate and quiet, the paddler eye-level with the reeds, capybaras watching from the banks, kingfishers flashing past. Three of the park's islands, del Cibo, Las Mangas, and del Barro, anchor the protected area. Fishing is permitted in designated zones, continuing a relationship between people and this river that long predates the park, in a region where artisanal fishing communities have always worked the water.

Predelta is best understood as a threshold. Downstream, the delta widens for hundreds of kilometers, eventually fanning out near Buenos Aires into one of the great river mouths of the world, a labyrinth of islands and channels covering an area larger than many countries. What the park preserves is the door to all of that: the first islands, the first splitting of the channel, the moment the Paraná stops being one thing and becomes many. For travelers it offers an accessible window onto a wilderness that is otherwise hard to reach. A half-day by boat from a small Entre Ríos town, and you are inside a living delta, surrounded by water finding a hundred new paths to the sea. It is the smallest of Argentina's national parks, yet it opens onto one of its largest natural worlds.