At a party one time someone unexpectedly turned to me and asked, "What was it like to snorkel in a submarine?"
Well, and I mean this in the strictest of technical senses, it sucked.
When we were cruising at periscope depth, with two locomotive diesels running at full power, the engines needed a lot of air. It all came through a twenty-inch diameter pipe sticking out of the water. There was a quick-acting poppet valve which slammed shut in a fifth of a second whenever a wave washed over the top of the snorkel, or whenever a diving officer lost control of his depth. The result was misery.
As we began to snorkel, we took a reading of the barometric pressure immediately after the Chief of the Watch opened the snorkel intake valve, and just before the throttleman hit the starter valve on the first engine. That gave us a reference level for evaluating the torture that followed. The gauges that we actually used to measure the pressure of the atmosphere inside the submarine were aircraft altimeters. We used those instruments since they were accurate, they were reliable, they were relatively cheap, and we could get them repaired and calibrated easily.
When the snorkel head valve slammed shut, the engine drew its combustion air from the boat's atmosphere. The effect on atmospheric pressure throughout the boat was as if we were climbing in an aircraft at 5,000 feet per minute. When the altimeter in the engine room showed an apparent 6,000 feet, the engines automatically shut down.
But usually, almost always, we got the head valve dry before the engine shut itself down. The instruments typically indicated an apparent altitude of between 500 feet and 2,500 feet when the head valve dried out and opened up. Sometimes we got as much as a 5,000-foot reading when the valve opened. Whatever the reading, air suddenly rushed into the boat when the valve opened. The air pressure in the boat then increased at a rate equivalent to aircraft descending at 10,000 feet per minute.
Are your eardrums hurting yet?
Legend has it that oldtimers who had served in these same boats in wartime preferred depth chargings to snorkeling. I think that was just talk. But snorkeling really did hurt.
Once we snorkeled from Puerto Rico to Cape Hatteras. Day after day we suffered, with no relief. We lapsed into a semi-conscious state each night in our bunks, but it can't be said that we slept. We had to clear our eustachian tubes constantly, around the clock, every couple of minutes or so. As we got closer to Hatteras, the weather got worse, and the snorkel valve stayed shut longer each time.
Antihistamines were quite popular with the crew. Many sailors learned to curse in their sleep.
When we got to Hatteras we surfaced, in some pretty rough seas. As I climbed to the bridge with the lookout, a lot of water entered the boat through the upper hatch. The two of us fastened ourselves to the bridge with two safety lines each. The hatch was slammed shut behind us. While the hatch had been open briefly, sea water had found its way into some of the electronic equipment below decks. The vacuum tubes did not like that at all. The skipper decided not to open the upper hatch again until the weather improved. That turned out to be eleven hours later.
So the two of us who were trapped on the bridge were cold. And we were soaking wet with the waves coming over us from time to time. And we got very tired from being slammed around by the waves, as we tried to hold on to the boat to keep from getting bruised, or worse. And we got hungry, and quite thirsty.
But at least we were no longer snorkeling.