By the Wikipedia definition a mermaid is a mythological aquatic creature with a female human head, arms, and torso and the tail of a fish. A male version of a mermaid is known as a "merman" and in general both males and females are known as "Merfolk" or "Merpeople". Mermaids are represented in the folklore, literature and popular culture of many countries worldwide.
1560, off the coast of Ceylon
An island in the Indian Ocean off the Southeastern Coast of India a group of Jesuits, along with the physician Bosquez (aide to the Viceroy of Goa) autopsied seven mermaids who had been found deceased earlier, and reported the mermaids were anatomically and spiritually identical to humans (minus the fishtail, I'm sure).
2009 Hafia –Israel
Dozens of people in the Haifa suburb have reported seeing a creature that resembles a young girl leaping out of the water and doing aerial tricks across the waves before disappearing to her home under the sea. The town's local council is offered $1 million to anyone who could prove the creature exists.
In 1990 a creature, which has yet to be categorised, was found in the Outer Hebrides, Scotland (UK) believed by some to be a mermaid.
Isle of Muck, Scotland (UK) 1977
Sandwood, in Sutherland, was once known as the 'Land of Mermaids' because of the number of sightings. The mermaid was described as the top half of the body resembling that of a European woman, whilst the bottom was said to resemble that of a fish.
25th Century Suffolk, England
In the twelfth century it was reported that a merman was caught by fishermen off the east coast near Suffolk, England (UK). He seemed unable to speak when released from the nets. The merman was taken to a church and even tortured but still not utter a sound. Described as 'the appearance of a man in all his parts' the merman quickly escaped when taken to the water supposedly to bath.