Yemaya is Goddess of the living ocean, some say Mother of all. An African Goddess. It is believed that she can cure infertility in women. The Cowrie shell represents her.
Yemaya is said to wear seven skirts, which represent the seven seas. She is said to be slow to anger, but when she does it is violent, think Tsunamis and other violent storms at sea.
With all of this in mind I imagine a huge - not fat, just a towering figure - mermaid type figure, wearing Cowrie shells in her hair. I see her rising up and engulfing ships, entire towns and causing a huge amount of damage once she is angered. But when she is being of gentle nature I see her sitting on a rock, far out to sea, basking in the sun and watching over those who worship her.