It turns out that fish communicate vigorously underwater! The young French scientist Bill Francois takes us into the abyss of the sea and deciphers the secret languages of its inhabitants - colors and sounds that are elusive to our sight and hearing, electromagnetic fields, smells, pheromones. Underwater life passes before the reader like an exciting film with subtitles written by the ocean itself. We will learn how the Atlantic cod discovered America, ahead of Christopher Columbus, and the Baltic herring composed a political thriller, how shellfish sing, and dolphins help people hunt whales. The author presents scientific information about the internal structure, habits and tricks of the inhabitants of the sea simply and with humor. Tuna, sardines, eels, anchovies, shrimp - all get a voice and tell their stories eloquently. And twenty-six-year-old physicist Bill Francois himself specializes not only in ichthyology and hydrodynamics, but also in oratory. In 2019, he won the eloquence competition on the French television channel France 2, and his speech received 10,000,000 views on the Internet. And this book, illustrated with drawings by the author, has been translated into 16 languages.