Twilight Lake in Bayhead, New Jersey, receives large volumes of surface drainage water from the Point Pleasant municipal area through an overflow drain entering the lake below water level. The lake is thus potentially at risk for diminished water quality from organic loading, as well as from pollutants such as oil, pesticides, etc. This study was carried out to determine whether input of surface water from the overflow drain to the lake has measurable effects on water quality. Data used to assess the quality of water included turbidity, depth, temperature, pH, nitrate content, dissolved oxygen, salinity, algal index, submerged aquatic vegetation, and wildlife observations. A second sampling site, the canal adjacent to the Bayhead Yacht Club, was sampled and used for comparison. The second sampling site was chosen because the water near the Yacht Club was not in the immediate vicinity of the drainage outlet, but was close enough to the original sample site to possess similar water quality characteristics. The second site is also the area where lake-water flows into the larger Barnegat Bay system. Beginning in March of 1999, samples were taken on an approximately weekly basis for a period of nine months. During this time, both sampling sites frequently displayed reduced dissolved oxygen levels, with near-surface oxygen concentrations often falling below saturation, particularly during the summer months. However, excessive nutrient inputs were not detectable and high levels of phytoplankton growth were not evident. Thus the cause of the observed hypoxic conditions could not be unequivocally determined. However, our preliminary results suggest that there is a potentially significant problem with water quality at this site that warrants further study.