The young merman Finn Flosse is an extraordinary inhabitant of the ocean depths. Since his father is a "bad" two-legged creature, meaning a human, and his mother is a beautiful mermaid, he looks a bit different from an average sea child. One day, after upsetting his stomach with a colorful, funny something, and when Herald the Herring gets caught in a "ghost net" set by humans, the fish suffer from stomach aches, and a huge, large, colorful wave, which is undefinable to him, invades the realm of sea creatures, little Finn Flosse gathers his courage and sets out with his friend Theo the whale to track down the mysterious something. The children's book Finn Flosse addresses a highly relevant and pressing issue. The masses of waste that we humans no longer want end up carelessly in the sea and harm the marine inhabitants. Finn Flosse takes action and fights against this.