This is a female of a non-human species called the Sarn that lives in oceans all over the world. They possess the ability to appear to human eyes as whatever that human expects to see. Thus, a sailor on a long voyage sees a naked woman with a fish tail, and a drowning man might see a dolphin pushing him towards shore. Sarn tend to be playful, inquisitive creatures. This is a rare look at a Sarn's true form, and even rarer, a Sarn that is pregnant.