I have a thing for creating creatures, I don't know if anyone will stop to read this, but here goes

Mosaic mermaids are sea creatures that live at shallow depths and far from the coasts, where they gather in groups of 5 or more individuals, hunt together and protect each other.

Their name is due to the scales on their fins, which appear to be a mosaic of different colors, helping them recognize each other in groups and find a mate. When a mosaic mermaid finds a mate and changes groups, or forms a new one, their colors change.

Their first sighting was by fishing boats, they mistakenly thought they were dolphins because of their sounds, and upon seeing them, they mistakenly categorized them as "mermaid dragons", that term was not fixed until many centuries later