I'll use my oc Janice

Janice: ~she was sitting on a bench looking at the lake ~

Janice: ~goes to a bathroom stall and changes into swim suit and jumps into lake and goes to very bottom and doesn't come up ~

Janice: ~after awhile she came up but she wasn't breathing heavily, she was breathing normally ~

Janice: ~nods ~ Yep!

Janice: ~ closes eyes and inhales and exhales slowly once and goes back under and she wasn't holding her breath ~

Janice: ~transforms under water ~

Janice: ~waves ~

Janice: ~she swam up and transformed back to normal ~

Janice: Okay then.. ~ she went to the bathroom stall again and dried off then changed back to normal clothes ~

Janice: Welp ~ sits on bench and leans back and falls asleep ~