unconventional mermaid
A mermaid or merman depicted differently from classical mermaids of the Disney variety. Common traits are a taur body, multiple and pronounced animalistic traits (sharp teeth, webbed hands, gills in uncommon places, extra fins), or being based on specific animals that aren't your average fish.
To qualify for this tag, a character must have a reasonable amount of these differences to be "unconventional". For example, just webbed hands or sharp teeth and nothing else are not enough.