The oceanographer Otto Janson summarizes the state of modern marine research in the early 20th century in his study. After providing an overview of the development and goals of marine research, he discusses its previous results. He focuses primarily on the global distribution of water and land, the properties of the seabed, ocean temperatures, and seawater movements, and finally on the plants and animals of the sea. This is a reprint of the original edition from 1914.