Below the main deck forward between the operating mechanisms for the Bow planes aft, and the Capstan and Anchor Windlass forward.
Aft of the bow planes mechanism are the air flasks that contain impulse air used to eject torpedoes.
Overhead you can see the small holes that allow air to escape during diving.
Below you can see the round shape of the pressure hull. You are standing above the torpedo tubes in the forward torpedo room.