Why do whales die when thrown into shallow water? Have military laboratories trained killer dolphins? Why are coral reefs rapidly dying out? What dangers does the ocean abyss store, and who is the enemy to whom: the ocean to man or the ocean to man? The second popular science book by A.N. Ostrovsky, published in the Animal Diversity series, answers these, as well as many other alarming questions of our time. It tells about the attitude of man to the inhabitants of the sea, about his role in the destruction and restoration of his resources. The author's goal is to make the reader think about the need to change our attitude towards the Ocean. This book is for those who love the Ocean and do not want it to turn into a lifeless water desert.