There was a diving officer’s checklist in the control room. What was that for?

When submarines were in port, the configuration of many of the valves was different. For example, some ballast tank valves were secured closed. That prevented accidental opening and submerging the boat at the pier. This was for the safety of the boat and the crew.

When going back to sea, that configuration needed to be reversed. The routine was that a sailor would use a checklist for a given space and set everything to the configuration that allowed to boat to submerge safely. Then one of the officers would use that same checklist to confirm that everything was set properly. At that point, the officer would notify the control room that the space was “rigged for dive.” Every space on the diving officer’s checklist had to be confirmed and marked before the boat would submerge.