My first skipper was nearing the end of his command tour. He was very cautious. We never took any chances, and we looked like the skittish old lady of the squadron. We had to admit that we were always clean and in good repair, but we were not the "hot runners" of the waterfront. All my training dives were made with this skipper. One of the things that he insisted on was that we pressurize the submarine and check for leaks before submerging.
After a few months, the new skipper reported aboard. He bit his tongue for the few days before he had assumed command and the old skipper had left. During this period he observed many things, including my performance as diving officer in training, and as Officer of the Deck (Surfaced) in training. When we went to sea next, he summarily declared that I was qualified to stand those watches, and my name was added to the list of officers who rotated through those watches.
He carefully plotted the next dive, to make sure that it occurred on my watch. He stood in the control room to observe. When the time came, a voice came up from the conning tower saying, "Bridge, this is the navigator. I relieve you of the deck and the conn. Submerge the ship."
The routine was unchanged since December, 1941. I yelled "Clear the bridge! Clear the bridge!" I sounded the klaxon twice. Both lookouts had already started down the ladders, using the technique in which no part of you or your gear touches the rungs. It is a lot faster that way. The instant the klaxon sounded, I heard the vents open, a sound that I had never heard before.
When the vents open, it allows air to rush out of the top of the ballast tanks, and 600 tons of sea water rushes in through the permanent openings in the bottom of the ballast tanks. These old diesel boats were designed before radar, and they were designed to submerge quickly as soon as a lookout spotted an airplane. They could be completely submerged in twenty seconds.
When I heard the vents open, I was startled, of course. I still had to descend two ladders to reach the upper hatch. After descending through that hatch, I had to pull the hatch shut so that it could be dogged shut. Once it was dogged, I was allowed to go down one more ladder to the Control Room, where I became the diving officer. My first task as diving officer was to check the board which indicated the status of all hull openings, and to call up to the conning tower, "Green board!" My voice was an octave higher pitched than usual.
As I was struggling to regain my composure, the skipper turned to leave the control room. As he left, he said, "We're a real submarine again."