The book provides a review of experimental methods and presents the worldwide newest literature regarding chemical substances fluxes via submarine groundwater discharge (SGD). Thus, the book characterizes both the distribution of chemicals in groundwater impacted areas in the Baltic Sea and their fluxes via SGD to the Baltic Sea. This book presents the state of art regarding the SGD and detailed studies on SGD characterization in the Baltic Sea. The Baltic Sea is an example of a region highly influenced by a variety of human activities that affect the ecosystem. It is shown that SGD has been proven to be one of the important sources introducing dissolved substances into the Baltic Sea. The loads of chemical substances delivered to the Baltic sea with SGD have not been quantified so far.