Soon after I was qualified to stand watch as Officer-of-the Deck, Submerged, we were somewhere between Palm Beach and the Bahamas, providing services while others used us as a sonar target for calibration of new devices and tactics on surface ships. When they woke me up for my watch, and I got to the control room, everyone was quiet. Too quiet.
When I looked around the small room it took me a while to notice that the shallow water depth gauge was disabled per standard technique, and we were using the deep water depth gauge. We were at a keel depth of 400 feet.
Then I climbed to the conning tower to assume the watch. We did the turnover of the operation plan, and I relieved George, and he called out to the quartermaster at his elbow (George was like that) and said, "In the quartermaster's notebook, Mr. Charlton has relieved Mr. Futch of the deck and the conn, submerged. Keel depth is 400 feet, and ..."
At that point George leaned over the hatch down to the control room and yelled, "Sounding!"
The answer came back, "Twelve feet!"
"... and depth under keel is twelve feet."
"Good night, Chuck."
"Good night, George."
Near the end of the watch we climbed to a keel depth of 100 feet. The old girl did a lot of grunting and groaning as the pressure on the hull eased.
When we got shallow, the crew started talking again.