The paper gives a historical review of groundwater flow research, and specifically, of research on the Baltic Sea groundwater flow. The previous investigations dealing with the problem are considered briefly. The author suggest a completely new approach to the study of groundwater flow, using the Finnish Gulf area as an example. The problem of groundwater flow in the Finnish Gulf is rather pressing, as nobody until now has given it due consideration. Subsequently, on the strength of the obtained data, new methods will be devised, aimed at the groundwater flow rehabilitation and the Baltic Sea waters protection against pollution.