Mia Efira Mark Seymon, a character from my comic book

Mia: The main character, always dreamy, with a rich imagination and an interest in mythical animals. She has curly brown hair, green eyes, slightly pale skin, but otherwise a normal human appearance with freckles. She also has an aquatic version, as she can breathe underwater. She has the same mermaid appearance as Efira, only with different colors and shades.
Water Mavka Efira: In human form, she is the same, just without the horns, scales, and tail. Her aquatic form: soft blue horns, dark straight hair, and blue eyes with constricted pupils. She loves to explore everything. She and Mia are best friends. She also has scales from half her eye to her right arm, a bushy tail, fins, and sharp claws.
​Simon: A calm guy with black, tousled hair and green eyes. He has a calm and reserved character.
​Mark: Curly and red-haired, also with green eyes. He has a calm character, always wants to be alone, but in company, he is cheerful and optimistic.
​Diana: Constantly envies Mia because she is treated better. Envious, but if you get to know her true character, she is cheerful, happy, and sweet. She has straight brown hair with bangs on her forehead, pale skin, and brown eyes.
You are the author, and you can change everything in them, but they don't care.
(I'm too lazy to come up with a story myself)

Only Mia and Evira can breathe underwater, and even if she draws water on herself, she will turn into a mermaid while the boys don't know about it.