the stern planes "outrank" the bow planes. They are larger/heavier. When the captain says "dive, make your depth 200 feet," the diving will order a down angle on the stern planes. "Stern planes, five degree down bubble, make your depth 200 feet." The stern planesman will call out ten or five foot depth increments ("dive...passing 100 feet") until told to stop by the dive.
Once the submarine gets to say 175 feet, the diving officer will order stern planes zero'd and then he will tweak the depth with the bow planes. From then on, the bow/fairwater planes will nudge the boat to the exact depth required. If the bow planes are unable to hold the depth, the dive will order water blown/flooded through the 24 inch main seawater valves. This gives him real time "hovering".
A boomer has to hover to launch missiles and fast boats need to hover for certain classified missions as well. All boats practice hovering as it is a skill that determines how good of a dive you are. The most successful dive will be the "battlestations dive". During battlestations the battlestations dive will become the diving officer irrespective of who is on watch.