Answer
Water has a high specific heat capacity, meaning that costal regions with lots of water are less effected by changes in temperature and have milder climates.
Work Step by Step
Because water has a high specific heat capacity, meaning that it takes a lot of heat energy to change the temperature of water. This means that in costal regions, the large amounts of water can absorb the large amounts of heat in summer without any large change in temperature, decreasing the temperature of the surrounding envinoment leading to cooler summers.
