The authors examine different data-supported methods for studying submarine groundwater flow and discharge through case studies contributed by leading international scientists. They discuss the maintenance of optimal water, salt, temperature and hydrobiological regimes of inland seas and large lakes. The book covers subsurface water exchange between the land and sea as well as groundwater discharge to the seas. It also provides a review of experimental methods and numerical modeling that can be used for the evaluation of specific discharge data and the effect of groundwater on the salt balance of seas and oceans. Defining the field of marine hydrogeology as a science that studies submarine groundwater, its properties, circulation, and distribution, delineates the role of quantitative assessment of subsurface water exchange between land and sea in predicting its changes under the influence of natural factors and human activity. It provides a framework for assessing different methods and making the best choice for various situations.