Of Triton is the second book to the Syrena series. A Syrena is another word for mermaid, but they do not like that word at all. Syrena is their species name. These books do go back and forth between points of views of the main characters. With it like this is helps on how they feel towards each other and if they are separated for a time ( which is most of the time since Galen- the main male lead- is in the water with his "country") to help what goes on, but don't worry the plot comes together in the end like it always does. Emma is a Half-breed, which means she can stay underwater for long periods of time without needing a breath of air.
Now in this book Emma finds out that her mother is a full-blooded Syrena and a princess at that. And since the Princess has been found, the kingdoms have to make sure that she is the princess and not someone posing as her. And so her is were Emma has to make a big life decision on weather to been known to the Syrena world.