Which substance you know well has the highest heat capacity?

Heat capacity is a physical quantity that characterizes the thermal properties of substances and is equal to the amount of heat that is needed to heat one kilogram of a substance by one degree.
Water has a high heat capacity. In the seas and oceans, water absorbs a large amount of heat, so this summer it is not very hot near the ocean, and in winter the water slowly releases heat into the air, and as a result, the winter is less severe.
Since water has a large heat capacity, it is used in heating systems, in heating pads, etc.