I believe that there are some parts here that may have been the source of inspiration for the new TV series by ABS-CBN: Dyesebel. In one episode it shows a coral which was in a form of a spear used to kill a fisherman. In one of the videos from Mermaids: The Body Found there were fishermen in the Baltic Sea and in other parts of the world who noticed how some fishes and whales have spears in their bodies.
If you ask me if there are evidences, I believe there are---it's just not enough yet. In our Evolutionary Biology class in college we talked about how man evolved and I must say that the evidences presented are plausible.
You shouldn't believe everything you see on youtube, but there are some worth thinking about. Below is the video of a boy who found a mermaid washed ashore. This was also part of the documentary by Animal Planet. The scientist who exposed the truth about mermaids, Dr. Paul Robertson, a marine biologist, was also part of the investigating team who studied what the Navy Team recovered the body found by the boy that day.
Below are the video clips from Animal Planet on Mermaids: The Body Found and Mermaids: The New Evidence
I don't think that this is a hoax. What I keep thinking about though is what Dr. Paul Robertson revealed about how Sonar Testing possibly kills them together with other sea creatures such as dolphins and whales. I think they should put a stop to this sonar testing. Of course, the global warming which causes an increase in the temperature of our seas possibly affects them too in the same way that we are affected by it. Yesterday was Earth Day, this should remind us to protect the Earth because it's not exclusive to us humans, we share it with plants and animals such birds and beasts of the earth, creatures the seas -- and mermaids too. One day, I believe when all the evidences pile up, they will finally stop becoming mythical creatures.