Before European traders arrived, African cultures had their own half-fish, half-human water spirits. But many water spirits looked like:

Hundreds of years ago, European sailors placed carved mermaids on the front of their ships as figureheads and told tales of sighting mermaids. Other cultures told their own myths of water spirits. When European ships arrived in Africa, people saw these mermaid figureheads and sometimes used them as models for their own water spirits. Later on, African slaves brought their water spirits to the Americas.
Before European traders arrived, African cultures had their own half-fish, half-human water spirits. But many water spirits looked like:
snakes
crocodiles
both
Over time, the European mermaid image blended with local stories and more and more spirits began to look like mermaids. These stories eventually merged into one powerful water spirit named Mami Wata. Mami Wata is often shown holding a snake.
The mermaid Lasiren is a powerful water spirit in the Caribbean. Like the European and African mermaids, Lasiren is often shown:
holding a mirror and a comb
playing the harp
both of these
She holds mirror to admire herself and a comb for her long, straight hair. Lasiren shares another feature with the African mermaid Mami Wata, whose legend was brought to the Caribbean by African slaves. Both water spirits wear modern, foreign clothes or accessories.
In Australia, the Aboriginal people speak of mermaid-like spirits called Yawkyawks. They have green hair that look like strings of:
snakes
seaweed
coral
Yawkyauks are ancient spirits that made the land, trees, and animals that still live in sacred water holes. They provide drinking water and rain so plants can grow. But if angry, they may bring storms. Some say Yawkyawks grow legs at night to walk on land, or even fly around in the form of a dragonfly!
In 1842, the famous showman P. T. Barnum announced in New York newspapers that a mermaid had been caught near the:
Indonesian islands
Hawaiian islands
Fiji islands
Barnum tricked thousands of people into paying money to see a fake mermaid. This grisly creature was made by sowing together the head and torso of a monkey and the tail of a fish. Created first in the East Indies, hundreds of fake mermaids were made for sale to British and American sailors.
Laurel Kendall, anthropologist
The mermaid is a good example of a form that looks familiar, while the beliefs behind it may vary from place to place. Cultures borrow inspiration from each other but also hold on to their own meanings.
After his voyage to the New World, Christopher Columbus reported seeing three mermaids near Haiti.
Columbus--probably glimpsing manatees--said they were "not as pretty as they are depicted, for somehow in the face they look like old men."
Stories of mermaids are not found in Arctic cultures.
The Inuit people tell of a powerful guardian spirit named Sedna. She wasn't described as a mermaid until outsiders brought stories and images of half-fish, half-woman creatures.
Distinct characteristic: Head and torso of a woman, tail of a fish
Other features: Often carries comb and mirror
Examples: European mermaid, Lasiren (Caribbean), Mami Wata (Africa), Sedna (Inuit), Yawk Yawk (Australia)
Significance: In different cultures, they are symbols of good luck (and sometimes bad luck), the world of the sea, fertility, and mother of sea mammals