My biggest problem was the writing. It wasn't bad, it was just written in a way that I couldn't connect to any of the characters and didn't care about what happened to them. Rio is constantly asking questions, to herself or to her Aunt, Maire.
"Hali's argument isn't without logic. But why wouldn't Bay tell me that she wanted to serve in the Above? Why did she ask me to promise to stay, and then leave?
Why trick me?
Was she afraid I'd be angry?"
Questions are constantly thrown at the reader.
"Why is she gone?
How did she die?
Who made it happen?
Nevio could have done it.
Or was it Maire?
It's not a thought I want to have, but it won't leave me.
Could Maire tell me if I'm the last siren?"
We're never shown anything, someone is always telling you what happened with constant info dumping. Rio rarely figures things out on her own, someone usually just ends up telling her.
Rio is so flat and bland. Her voice is always described as being emotionless and flat, so that is how the story is written as well. She always seems so cut off from everybody that I was never convinced that her and True could really have feelings for each other.
The only reason I continued reading was because I wanted to know why Rio's sister decided to go Above.
I liked the idea behind Atlantia, I just wasn't a fan of how it was executed, and the writing was definitely not for me. I guess the writing kind of goes with the atmosphere of living underwater, but it still wasn't enough for me to get engaged.
Honestly, the only "character" I enjoyed were the bats. I loved the bats.