Coral by Sara Ella

So, this book deals quite bluntly with themes of suicide and depression. If these are issues you have difficulty with please be careful when reading this book.

It's wonderful but very intense at points.

Oh, this book. Would you believe I almost didn't finish it? I'm so glad that I did.

Here's what's happening in this book.

Coral is a young mermaid whose culture considers emotions a disease. Her older sister fell in love with a human and is now waiting to die of the horrific Red Tide

Brooke is staying at an inpatient care facility for her depression and is struggling over painful memories.

Merrick is struggling with his domineering father, his depressed kid sister, and his mother leaving.

So spoilers.
I figured out the twist fairly early in the book but your mileage may vary.

Coral is Brooke. Brooke is Coral. Foxy is Rob.

The Coral story was what Brooke wrote to help her face her pain, which is why a mermaid would be able to walk into a small town and enter high school with no documentation.