Equal masses of dry sand and water absorb the same amount of heat in strong sunlight. The sand's temperature rises far more than the water's because

Core Concept

From q = mcΔT, a sample's temperature rise is inversely proportional to its specific heat when heat and mass are equal. Water's specific heat of 4.18 J/(g·°C) is several times larger than sand's, so the same energy input moves water's temperature much less. The water stores the incoming energy with only a small temperature response. This is why beach sand burns your feet while the adjacent surf stays comfortable.