Water parameters are essential in maintaining the good health of aquatic organisms. Fluctuation in any of the parameters is a stress factor for the organisms. Among them, salinity acts as a significant factor in stress. Zebrafish have substantial stress responses to variations in salinity, which cause changes in physiology and behavior. Fish experiencing fluctuations in the salinity content of their aquatic surroundings are said to be experiencing salinity stress. Excessive salinity can dehydrate freshwater fish and lead to an imbalance in ions; however, abrupt salinity reductions in saltwater fish can induce an influx of water and a loss of ions. Fish exposed to prolonged salt stress are more sensitive to illness, have lower general fitness, and have a lower chance of surviving. The acute toxicity and chronic effects of extreme salinity 6g/L,7g/L,8g/L,9g/L, and 10g/L are effectively seen in Zebrafish's heart tissue. This study enlightens how water quality parameters like salinity affect specific physiological and molecular events in Zebrafish. In summary, exposure to sub-lethal salinity concentrations influences Zebrafish physiology, resulting in mortality.