Wikipedia
A jengu (plural miengu) is a water spirit in the traditional beliefs of the Sawa ethnic groups of Cameroon, particularly the Duala, Bakweri, and related Sawa peoples. Among the Bakweri, the name is liengu (plural: maengu). Miengu are similar to Mami Wata spirits.
The miengus appearance differs from people to people, but they are typically said to be beautiful, mermaid-like figures with long hair. They live in rivers and the sea and bring good fortune to those who worship them. They can also cure disease and act as intermediaries between worshippers and the world of spirits. For this reason, a jengu cult has long enjoyed popularity among the Duala peoples. Among the Bakweri, this cult is also an important part of a young girl's rite of passage into womanhood.