The book presents the first comprehensive description of parts of the Mid-Atlantic ridge subject to a contract for polymetallic sulphide exploration between the International Seabed Authority and the Ministry of Environment of the Republic of Poland. The state-of-the-art of the study area presented here takes into account a variety of aspects, including hydrological and meteorological conditions, hydrography, optical properties of water, seafloor morphology, geology, sediments and sedimentation processes, pelagic environment and its biocoenosis, benthic organisms, seabed communities, deep-sea environmental protection, as well as many other. Also, the research methods and tools are enumerated, and the studies advised for the future are outlined. The Atlantic seabed area described in this monograph is situated near the central part of the Mid-Atlantic Ridge (MAR), one of the major geological formations on Earth, featuring - like other mid-oceanic ridges - active and inactive hydrothermal vent fields with their unusual and unique ecosystems. The commercial interest in MAR exploration is due to the deposits of massive polymetallic sulphides, formed as a result of hydrothermal fluid precipitation.