Seen from space, our planet looks like a beautiful blue ball where water covers more than two-thirds of its surface and forms the oceans and seas. Would you like to know if there has always been water or what navigation was like in other times? Can you imagine what an ocean is like inside or by whom its depths are inhabited? Do you want to know how we can take better care of our seas? In this book, you will find the answer to these questions and many others. Are you brave enough to venture in?