Youtubeville is very concerned about side effects and whether or not you can reverse it. Word has it weak legs are a sign its working and getting wet is oh so important. Getting submerged in the bathtub counts, but I imagine being a mermaid in the bathtub creates more problems than it solves.
Also, 100% of Youtube comments are either "THIS SPEEL NO WOERK!!! HOW DO" or "THEIS SI TOTALY FAKE!" or "THIS IS REEAL ITS UR FAULT FOR NOT BEIELVING IN MAGIC TO NOT WORK".