The opening of the text sets the stage for exploring the vastness and richness of oceanic life. It begins with a preface that hints at the author's passion for the marine sciences and his intent to share his knowledge after his passing. The initial chapters offer a general overview of the ocean's properties, touching on its coverage of the Earth’s surface, the significance of various oceans, and the dynamics of water movement and marine life. Through a blend of poetic descriptions and scientific observations, Moquin-Tandon prepares the reader for a deeper understanding of the creatures that inhabit the sea, their roles within the ecosystem, and the intricate relationships that flourish beneath the waves. (This is an automatically generated summary.)