Mehmaid. 
 I'm not a huge merfolk reader, but I did enjoy the merfolk aspects of the book. I liked the Greek mythology,the two leading characters and their story. I also liked how they weren't actually 'mermaids'. 
 I didn't care for the way the insta-love was done, the info-dumps or the way things were conveniently dropped into the plot to explain things or help out the characters. It did feel a bit young - as in written by a young person or a book that could use some style editing. 
 Overall, a YA book written with a heavy YA voice that many merfolk readers will probably enjoy.