This study examines the figure of Mami Wata and of "water spirits" or "sirens," first as myth, folklore, iconography, and cult practice (Atlantic Africa, diaspora), then as a recurrent motif in the popular theology of deliverance in certain charismatic and revival churches (West and Central Africa, the Caribbean, the European diaspora). Drawing on peer-reviewed academic sources (Drewal, Salmons, Meyer, Rey, van de Kamp, Homewood, Asamoah-Gyadu, Bernault, Tonda) and public documents, the article distinguishes documented facts from allegations, refuses any conflation with institutionalised classical Pentecostalism, and proposes a Protestant framework of discernment that holds together the biblical critique of false spirits and the pastoral critique of spiritual hold monetised through demonic diagnosis. A case study addresses the circulation of the "Gabonese siren" and of a letter attributed to Jacques-Yves Cousteau, treated as a documented apocryphon and not as proof of a demonic aquatic world.