Which parameter of the hydrosphere always remains constant?

density vs. depth at low latitudes

surface temperatures from low to high latitudes

temperature vs. depth at low latitudes

temperature vs. depth at high latitudes

Temperature vs. depth at high latitudes  of the hydrosphere always remains constant

Explanation:

There is a certain trend followed in the temperature and the depth of the water bodies. As the upper layer of the water heats from solar radiations, the temperature of the water seems to decrease with an increase in the depth and this trend remains constant at higher latitudes as well. All other parameter does not remain constant as there are minor or major changes observed in them. Changes are also observed due to changes in the latitude of the given water body.