Water has a high specific heat capacity. This allows water to moderate the climate of Earth by moderating large temperature changes. The ocean absorbs 1000 times more heat than the air does. What this does is in the winter months, coastal areas experience warmer temperatures due to the heat released to the atmosphere from the ocean. Because water is slow to absorb heat and slow to release that heat back to the atmosphere, it serves to moderate the Earth's climate. Water causes the temperature changes between seasons to be a gradual thing due to its high specific heat index.