Why Doesn't Water Freeze Deep, Deep In The Ocean?

It's just like why deep water is cooler than shallow water subjected to the same temperatures. sure at the surface it's all the same temperature give or take. the cold water, when there is no mixing, will sink down to the bottom. cold water is more dense. water has it's greatest density at 4 degrees celsius. therefore water at this temperature will sink the lowest. also, ocean...salt water. salt water freezes at a lower temperature. and as to the moving water theory. i would think that deep in the oceans where little mixing occurs, there would be less of a current. the bottom simply is not subjected to the cold atmosphere that the top is.