on a full moon touch some kind of form of water and look at the full moon for 30 seconds then the next morning touch some kind of water and you might just become a mermaid/merman
If you have a pool swim in it on a full moon and then the next day when you are in your pool you are a mermaid
touch water on a full moon. (warning DO NOT DO THIS AFTER YOU ARE A MERMAID. side effects may include, a sudden need to cause trobule, turning into a siren witch is a evil mermaid that attracts boys with her angelic voice.) Hope you are with your powers!