A water dwelling race, that eats other ocean creatures (and the occasional human), mysterious and tend to hoard the secrets the ocean reveals. They could be considered a sister race to the Fae.

Mer

Medium to heavy muscled, not too heavy not too thin.

Extremely light. Sirens live in the deep ocean and tend to not see sunlight often. Sirens who live on land never tan in the sun, only burn.

Medium to Tall. Always above 5'5.

Are nearly always their perfect weight, as they have great appetites and are always swimming.

Mostly human looking on land, unless provoked, which can cause fangs and teeth and eye changes/scales, to appear. In the water, they have magnificent and strong tails, and glowing green eyes. They have fangs and claws for tearing into prey.

There's much variance in tails and hair color. Height is pretty variable as well, with everyone ranging anywhere over 5'5

Very little. The minimum needed to hide important bits. Too much clothing can interfere with swimming and feels weird against scales.