A major problem in coastal oceanography is the lack of knowledge of the spatial and temporal scales at which water masses of various origins interact within the coastal zone. While their gross characteristics may be known, the smallscale, two-dimensional, horizontal variability of water mass properties cannot be adequately determined using conventional oceanographic measurement methods. Typically, these small-scale variations are measured in one dimension, if at all, using conventional techniques and usually at great expense. Thus many key parameters necessary for the characterization and quantification of important physical, chemical, and biological processes in the coastal and estuarine regions remain unknown. A prototype instrument that promises to remedy this situation for the parameter which most influences the hydrodynamics of runoff-influenced coastal regions (i.e., salinity) is now available.