Serenephobia

Serenephobia (from Latin serene, "mermaid") is the fear of mermaids. Although there is no proof of existence of these aquatic humanoids, people allegedly see mermaids and even captured on camera. Young children can suffer this phobia when first hearing about mermaids in folklore, while adults can suffer it after first hearing about the reports of real-life mermaids. Sufferers would avoid going in the seas, lakes or rivers as they're afraid that mermaids may pull them underwater and drown, but sufferers can go in the swimming pool where water is clear and shallow covering a small area.

The phobia is treated by teaching them that there are few to no documented cases of people getting injured from mermaids and that mermaids are not proven to exist.