Remote sounding of the atmosphere is a well-established method used extensively used extensively for operational weather forecasting and scientific research. Active or passive instruments carried on satellites (or aircraft) can measure profiles of temperature, pressure, trace gases, and particulate matter.
Is anything similar possible for a ship sailing on the ocean? What methods exist, in theory and in practice, to remotely sense a profile of temperature, density, salinity, etc., from the ocean floor to the ship? Or can such profiles only be obtained in-situ?