details the functioning of sensors and instruments used to assess the following parameters in oceanography: temperature, conductivity, pressure, sound velocity, current in magnitude and direction, time and position with GPS, height of water and tide, waves, optical and chemical properties (turbidity), dissolved gas (O , CO ), pH, nutrients and other dissolved elements. Furthermore, this book also elaborates on the different means used to obtain measurements at sea (boats, drifting floats, moorings, undersea platforms, gliders…) and techniques currently being developed.