The possibility of salt-water encroachment into the aquifers of the Coastal Plain of Delaware from saline-water bodies (Chesapeake and Delaware Canal, Delaware Bay, Atlantic Ocean) has received considerable attention (e.g., Sundstrom et al., 1967, 1971, 1976; Woodruff, 1969). These authors have shown that, so far, little encroachment has taken place. It is also known that a large body of highly saline water occurs at depth beneath the Coastal Plain (Upson, 1966; Back, 1966; Brown and Reid, 1976) and the adjacent continental shelf, but no reports have been published about its origin and shape, and the salinity distribution and flow pattern within it. Yet, this saline-water body has a bearing on the development of fresh-water resources throughout Delaware, the feasibility of constructing injection wells for the disposal of liquid wastes, and radioactive waste disposal in the crystalline rocks beneath the Coastal Plain sediments, and upon the occurrence or migration of hydrocarbons (Bredehoeft and Maini, 1981). It is, therefore, important to study this body of saline water.