Deep waters are "formed" where the air temperatures are cold and where the salinity of the surface waters are relatively high. The combinations of salinity and cold temperatures make the water denser and cause it to sink to the bottom.
The Gulf Stream carries salt into the high latitude North Atlantic where the water cools. The cooling and the added salt cause the waters to sink in the Norwegian Sea. This is the formation of Atlantic Deep Water
Places where the water is cold enough and salty enough to form bottom water.