I know that water is the most dense at 4 degrees celsius. That's why water at the bottom of a sea has that temperature. But how did it get that temperatur in the first place and why does the energy not distribute itself in such a way that the temperature is the same throught? Is it the particles that have a temperature of 4 degrees that sinks to the bottom or is it the pressure at the bottom that makes the water more dense? What if a sea is surrounded by constant weather condition and constant atmospheric temperature. How would the temperature distribution look like as a function of altitude under water? If the surrounding temperature is 20 degrees, would the water at the bottom if it is deep enought still be 4 degrees?