A young, enthusiastic student of marine life takes the readers on a quest to discover the fantasy creatures that live in the sea. The children will read her diary, filled with information, legends and details. Tips are also intended for all sea life lovers to do their part and keep the ocean clean and defend the kingdom of its creatures that today, more than ever, is threatened by dangerous, irresponsible behaviour.

Two sections dedicated to the underwater creatures: those who live on the surface and those who live in the abysses.

Short, fun, approachable stories that describe each creature and explain how to catch sight of it, how to tame it and what makes it angry

At the end of the story, the readers will find a short test, similar to the one the book's narrator must take, so that they'll get their Certificate of Fantastic Creatures Keeper, that children can detach from the book and fill in.