Ehhh... 
 This wasn't "bad" but it was pretty dull. 
 It felt like not much was happening when stuff was happening. The whole focus of the story was on a city that the main character couldn't wait to get away from... sooooo why should I care about its fate? I thought the plan was to get away yet now we are saving it? 
 The romance was just as dry. I'd explain further, but there isn't much to work off of ...and I think that's exactly why it failed. Zero personality. Zero chemistry. Flat. 
 Also some elements felt a little random. Why robot fish? Why bats? How did these relate to the story at all? The weird choices kept pulling me out of the story because they felt exactly like weird choices. 
 It was a little hard to take anything seriously after so many "lol what??" moments ...including the concept behind these sirens and the entire plot that followed. 
 I actually don't know what kept me going. But I finished it and will soon forget.