They are beings whose upper half of their body is similar to a beautiful woman and from the waist down does not have limbs but a fish tail. It originates with Greek mythology, although they have also been present in the folklore of other civilizations. They have gone from mythological to folklore or legend and to popular beliefs. Which has been demonstrated by various sightings over the centuries and in the same way has been decreasing as scientific knowledge progresses, so superstition has receded.