A groundwater level survey and reconnaissance of the hydrologic conditions in the South Coast aquifer in the Santa Isabel area of southern Puerto Rico was conducted during March 31 to April 17, 2014. The field survey included groundwater level measurements at 55 wells and instantaneous streamflow measurements at 15 locations in streams and irrigation canals. A potentiometric surface map of the alluvial aquifer provides an indication of the directions of groundwater flow. The objective of the field survey was to delineate the potentiometric surface of the study area defined as the South Coast aquifer between the Río Descalabrado to the west and the Río Jueyes to the east of the town of Santa Isabel. Instantaneous streamflow measurements were made at selected sites along the Río Coamo, Río Descalabrado, Río Cañas, and the Canal de Juana Díaz to evaluate groundwater and surface-water interactions during the synoptic survey. Potentiometric contours are based on water-level measurements collected at wells during the dry season from March 31 to April 17, 2014. Measured values of the potentiometric surface ranged from -22.80 feet to 185.4 feet above mean sea level. The results of the study indicate a cone of depression in the aquifer near the center of the study area, where the potentiometric surface is below mean sea level.