The book of Professor Lev Alexandrovich Zenkevich tells about the history of the study of the life of the seas and oceans, contains basic information about the animal and plant world inhabiting our seas. It reveals the patterns of distribution of marine organisms, provides information about the benefits and harms of them, and about the prospects for the economic use of marine fauna and flora. Almost every page of the book contains an informative illustration. The publication is recommended to all lovers of nature and geography.