"Oshun is the Yorùbá Orisha (Deity) of the sweet or fresh waters (as opposed to the salt waters of Yemaya). She is widely loved, as She is known for healing the sick and bringing fertility and prosperity, and She especially watches over the poor and brings them what they need. As Orisha of love, Oshun is represented as a beautiful, charming and coquettish young woman. In some tales She is said to be a mermaid, with a fish's tail.
The Yorùbá clans inhabit parts of western central Africa, in present-day Nigeria. Oshun is the Goddess of the river of the same name, and She is especially worshipped in river-towns. During Her yearly festival, She is said to choose one or more women dancers to descend into (much like participants in Vodou ceremonies may be "mounted" or "possessed" by a Lwa). These women then take new names in honor of Oshun and are thereafter consulted as healers."
- from ThaliaTook.com