The relation between the water temperature and depth of the water is inversely proportional.
Let water temperature be t and depth of water is d.
The relation is written as
here k is the constant of proportionality .
For the depth of water 1000 m , the temperature is 9° Celsius.
Thus the value of constant of proportionality k is 9000.
For depth of 800 meters , the temperature of water is
Therefore, the temperature of water with depth of 800 meters is 11.25 degree Celsius.