Establishing Merman Powers In-Story?

[SeaMansa]

So I am finishing up a script, and just ran into a bit of hole. I really don't know a good way to introduce the fact that my main character has acquired magical ability. This scene wasn't apart of my original idea so idk really how I should go about it.
In most mermaid media, the character usually takes a shower and boom, tail. I am not going with that. I just need some casual, everyday event where in this case, something strange happens because of their new powers. Can anyone give me an idea or suggestion.

I've been making so many changes that my brain power is kind of run down :(

[cletusk20]

Maybe rather than growing a tail, he finds himself swimming and gets into trouble. And in his panic, he accidentally starts water breathing. Which would show that he has powers. Just a thought.

[SeaMansa]

Good idea, but I've already got something similar for when the tail finally comes out :(

[Mermaid Jaffa]

Or when he gets upset, he causes earthquakes, and walls of earth to rise up.

[SeaMansa]

hmmm....that's a good idea.

[Trade Winds]

I am kinda torn when I write about doing the whole 'dangerous situation and suddenly new powers save me' thing. I am ALWAYS worried I might have a Mary Sue/Gary Stu thing going how no matter how fcked up my char's lives are. But in generally it's the best way to get powers to manifest short of having a char kidnapped and turned into a science experiment.

One of my favs way is the char is loving among humans, one of their species finally finds them and guides them thru the powers. But all these ways are so overused in writing (young adult fantasy for example *shudder*) that *I* try not to do it so often. But it is YOUR writing so you do what you like best. The rest is just an old writer expressing her thoughts.

If you ever concerned your character is TOO special...I love this Mary Sue/Gary Stu test http://www.springhole.net/writing/marysue.htm

Tl;dr based on how you will have the tail manifest with a dangerous situation, maybe have the powers occur at the same time to streamline it, unless you want to draw out him discovering all his abilities