I am very skeptical of stories that depict mermaids as beautiful, wonderful, gentle creatures who live in the sea.
Think about the Greek syrens. Some say they were winged women, but some other sources say they were half fish. They sing, sailors hear them and, with the crew entranced, the syrens sink the ships. Why would they do that? Maybe they eat the sailors afterwards. According to Japanese mythology, on the other hand, eating mermaid meat gives you eternal life.
If after reading these bits of information you still want to think they are lovely, I don't know what to say.
And they don't have to be half fish, connected at the lower waist so that the result looks the sexiest. Why can't there be 30:70 or 20:80 human:fish combinations?
You might say I am jealous of beautiful mermaids. You might be very right.