Mermaids are mythical creatures, half woman and half fish. With the notable exception of cruel experiments performed on undeserving people, it is impossible for humans to become half fish. Even so, with a bit of money and luck, a person can become a professional mermaid.
Professional mermaids are actresses who tap into the mystique of being a mermaid by wearing a costume specifically created to withstand long term exposure to water. Depending on their profession and location, they may swim with children at parties, tend aquatic wildlife or be a decorative performer at parties, bars or any number of places with an aquatic theme. There are a number of places to purchase mermaid costumes, specifically tails that can be used in water, but they are not cheap. Once they have been obtained, however, the performer has a variety of options, and can even go into modeling, if longer performances are something she finds herself incapable of or unwilling to do.
The myth of the mermaid is a far-reaching one, primarily localized to fishing and boating cultures. Though the myth has died out, mermaids were known as being alternatively benevolent and terrifying, sometimes luring men to their death, and other times, rescuing men in danger. Historically, many goddesses, major and minor, have been known as mermaids, and they hold an unshakable place in the cultural consciousness of our world.