A brackish environment is a place where freshwater and saltwater mix, such as an estuary or a mangrove swamp. The salinity of this environment varies depending on the amount of freshwater and saltwater present. During the rainy season, there is usually an influx of freshwater, which dilutes the saltwater and reduces the salinity. Therefore, the salinity of a brackish environment tends to decrease during the rainy season. On the other hand, during the dry season, there is less freshwater and more evaporation, which leads to an increase in salt concentration and an increase in salinity. Therefore, the salinity of a brackish environment tends to increase during the dry season.