The Amazon River meets the Atlantic at a river delta where archaeologists work on Marajó Island, digging into the remains of a culture that thrived at the river's mouth centuries ago and left behind artifacts whose full story is still being pieced together. The film follows their excavations alongside footage of the delta itself, where fresh water and salt water mix into one of the more productive ecosystems in South America, supporting fish, birds, and plant life that depend on that exact collision of river and sea. It tracks how people living in the delta today work with and against that environment, fishing and farming a landscape that floods and shifts with the seasons. The film treats the archaeology and the ecology as one subject: a delta shaped by thousands of years of human presence as much as by water and silt, and now facing pressures, from development to environmental strain, that threaten to unravel that balance before all of it is even understood.