Answer:
Due to high specific heat capacity of water as compared to land
Step-by-step explanation:
The specific heat capacity of water is much higher as compared to land. Specific heat is the amount of heat required to raise the temperature of anything by a unit degree ( of either Celsius or Fahrenheit).
Thus, water in ocean and coastal areas take much longer time to heat. In the same way coastal areas need much longer time to release the absorbed heat. Thus, the temperature is coastal area is more or less stable as compared to non coastal areas where cooling and heating of the atmosphere takes place quickly.