The perception of temperature is influenced by various factors, including the body's physiological response, heat transfer mechanisms, and sensory perception. In the scenario you described, where a pool or lake at 80 degrees Fahrenheit feels cold while the air temperature at the same level feels hot, the phenomenon can be explained by the process of heat transfer.
When you enter a pool or lake, the water conducts heat away from your body more effectively than air. Water has a higher thermal conductivity than air, meaning it can transfer heat more efficiently. As a result, when you immerse yourself in water at 80 degrees Fahrenheit, the water rapidly absorbs heat from your body, causing a sensation of coldness.
On the other hand, when the air temperature is 80 degrees Fahrenheit, the heat transfer between your body and the surrounding air is less efficient. Air has a lower thermal conductivity compared to water, so it doesn't extract heat from your body as rapidly. Instead, your body's natural cooling mechanisms, such as sweating and evaporation, are more effective in dissipating heat into the air. As a result, the air temperature of 80 degrees Fahrenheit feels hot because your body's cooling mechanisms are less effective in this situation.
In summary, the perception of temperature depends on the efficiency of heat transfer and the body's ability to cool itself. Water at 80 degrees Fahrenheit feels cold because it conducts heat away from your body more effectively, while air at the same temperature feels hot because it hinders the body's natural cooling mechanisms.