A Who's Who of World Mythology : Apsu

In Babylonian myth, Apsu or Apason (from the Sumerian Abzu) was the primeval abyss of sweet water from which all things sprang. She was the Akkadian version of Tiamat, but with the decay of matriarchal ideas, she became the husband of Tiamat, goddess of the primeval salt waters. As the two waters mingled, they gave birth to Mummu, the Waves, Lahmu and Lahamu, and Anshar and Kishar (the parents of Anu and Ea). The first men were formed by Nammu with clay dug up from Apsu’s waters.

According to the Babylonian creation epic, Enuma Elis, Apsu plotted the demise of the younger gods and was killed by Enki (Ea) as he slept. Enki (Ea) captured Mummu and set up his abode, Ezuab (House of the Apsu), over the oceans. This triggered the battle between Marduk, the son of Enki (Ea) and Tiamat. Through their bloody battle, the world and sky was formed.