Cold, salty water is dense and sinks to the bottom of the ocean while warm water is less dense and remains on the surface. ... Water gets colder with depth because cold, salty ocean water sinks to the bottom of the ocean basins below the less dense warmer water near the surface. In other words it takes a lot of energy to heat water. The specific heat of land is much lower than water. It varies a little by soil type, but it takes a lot less energy to raise the temperature of the same amount of land as water.