Water has a high specific heat which causes it to gain heat very slowly. Specific heat is the amount of heat per unit mass that is required to raise the temperature by one degree Celsius.
The specific heat of water is 4.186 joules/gram Celsius, which is higher than any other common substance. It is higher than that of a metal.
The high specific heat of water is due to hydrogen bonding among water molecules. These bonds create a phenomenon where it takes a relatively large amount of heat to gain just 1 degree Celsius change in temperature.
