Tiamat is a Babylonian goddess of the ocean who gave birth to sea creatures. Although she is often described as a sea monster (a multi-headed dragon in Dungeons & Dragons game), there is no ancient text to corroborate that.
In fact, in Enûma Elish which is the Babylonian creation myth, her physical description includes a tail, a thigh, "lower parts" (which shake together), a belly, an udder, ribs, a neck, a head, a skull, eyes, nostrils, a mouth, and lips. Inside she has a heart, arteries, and blood.
So, I made her look like a mermaid. :) I want boobs like that. :)