Water does not give up or take up heat very easily. Therefore, it is said to have a high heat capacity. In Colorado, it is common to have a difference of 20˚ C between day and night temperatures. At the same time, the temperature of a lake would hardly change at all. This property originates because energy is absorbed by water as molecules are broken apart or is released by molecules of water associating as clusters.
Video: Heat Capacity of Water (01:13)
Take a few minutes to watch the video below to help you understand heat capacity.