In July-August 2022 an algal bloom on the Oder river resulted in an environmental disaster. It led to a severe damage to the river’s ecosystem, some reports of health issues of the human population in the area as well as (inevitably) to mild tremors in local political landscape. A simple collective action of microscopic unicellular organisms led to their aggregation and rapid reproduction, which resulted in massive macro-scale repercussions of complex nature – a vivid example of what can scientifically be described as emergent phenomena in collective dynamics.