One famous painting by John Waterhouse, called “The Siren” depicted sirens as being sea maidens, which eventually caused a great deal of confusion, though this is not the only reason. Sirens, like harpies in form, though polar opposites in threat, were birdlike, and avian, but very beautiful with seductive voices. Sirens were always portrayed as having great beauty, unlike harpies, which were originally depicted as being very, very ugly, and sometimes as having snakes for hair, like the Gorgon Medusa. Though the belief is inaccurate, sirens are usually portrayed as mermaids, even today when we have the benefit of actual clarification.
The reason for the tangle was also language, –the word for mermaid, in most of the prime European languages, such as Spanish, French, Italian, Polish, Romanian or Portuguese, the term for mermaid is Sirena, Sirčne, Sirena, Syrena, Siren? and Sereia so that the traditional Greek sirens, when translated into English, become beautiful women with the lower bodies of large fish. Sometimes sirens are portrayed more traditionally as having both bird and lion qualities, though with radical deformities not visible from long distances, –such as a larger than average human head. In their lion and bird hybrid depiction, they also resemble the sphinx, though sirens are only usually depicted as having a mane of the lion. A sphinx has a lion’s body, and a bird’s wings, so that there is still a difference though small.
Sphinx may even have been more of a catch all general term for human animal hybrids that incorporated avian features in Greek, –since more often than not, these creatures were malignant. So, to further clear any confusion, there are traditionally three sirens, the same number of harpies, though they have different weapons of choice, they are both avian monsters. also, sirens are only portrayed as mermaids due to a trans-lingual confusion of homonyms, –sirens are bird women, not fish women!