There are many arguments saying that the Mermaids are real, somebody published some videos as proof claiming that they caught it on tape, but also there are arguments against it saying doubting its credibility.

Wikipedia about Mermaids

A mermaid is a legendary aquatic creature with the upper body of a female human and the tail of a fish.^[1] Mermaids appear in thefolklore of many cultures worldwide, including the Near East, Europe, Africa and Asia. The first stories appeared in ancient Assyria, in which the goddess Atargatis transformed herself into a mermaid out of shame for accidentally killing her human lover. Mermaids are sometimes associated with perilous events such as floods, storms, shipwrecks and drownings. In other folk traditions (or sometimes within the same tradition), they can be benevolent or beneficent, bestowing boons or falling in love with humans.

Some of the attributes of mermaids may have been influenced by the Sirens of Greek mythology. Historical accounts of mermaids, such as those reported by Christopher Columbus during his exploration of the Caribbean, may have been inspired by manatees and similar aquatic mammals. While there is no evidence that mermaids exist outside of folklore, reports of mermaid sightings continue to the present day, with recent examples from Canada, Israel, and Zimbabwe.

Mermaids have been a popular subject of art and literature in recent centuries, such as in Hans Christian Andersen's well-known fairy tale "The Little Mermaid" (1836). They have subsequently been depicted in operas, paintings, books, films and comics.