The River Runs Red is an interactive documentary exploring the world’s largest tailings disaster in Brazil on the Rio Doce, seeking to explore how to perceive slow violence in the river for both humans and more-than-humans through a poetic dialectic of new attunements. This project combines two core ideas. First, the site of the Rio Doce is crucial for investigating the long and multifaceted history of slow violence that spans the centuries before and after the disaster. Second, the project proposes experimental documentary film, combined with an experimental interactive interface as an embodied, sensorial, emplaced approach for capturing the long now of slow violence. How can interactive documentary rethink narratives of slow violence – for both humans and more-than-humans – through the figure of water? This chapter will span the importance of thinking with water, of defining multispecies cinema, of several water-based interactive sound, web, and VR projects, and end with a thorough review of the Rio Doce disaster, the violent colonial history that serves as the backdrop for the disaster and future of the region, and the methods behind the interactive film project The River Runs Red.