Submarines: "Loss of Sea Legs"?

Approximately half of the astronauts in the U.S. space program have suffered from space sickness.[5]

The most recognized theory for the cause of motion sickness is that it is an ancient defense mechanism against neurotoxins.[6] The brain's area postrema induces vomiting when poisonous effects are detected, such as feeling but not seeing motion (for example, in a ship with no windows). The inner ear transmits a sense of motion while the eyes transmit a lack of it. As a result of the conflicting signals, the brain concludes that one of the signals is hallucinatory and possibly due to ingestion of poison (astronauts may be most familiar with excess alcohol consumption; for still others the cause may be toxic mushrooms or spoiled foodstuffs). The brain's best defense is to induce vomiting to eliminate the supposed toxin.

Motion sickness or kinetosis is variously referred to as seasickness, carsickness, carsickness, simulation sickness, airsickness, or space sickness. Dizziness, fatigue, and nausea are the most common symptoms of motion sickness.

A legendary submariner had this to say:

...Take, for example, the trip across the English Channel. No other water journey causes an equal amount of suffering. The most hardened traveller becomes seasick there. - John P. Holland (April 22, 1901)

- Holland, John P.,"The Submarine Boat and its Future," North American Review, December 1900.

After WWII, Submarine Medecine Practice proclaimed this:
18.7.4. Ship's motion.
Seasickness is caused by periodic acceleration on undetermined receptors in the inner ear. Certain factors as the type of ship and state of the sea are important, and the fact that most of the submarine crew are crowded below decks while the ship is on the surface might be contributory. The submarine's roll is believed to be gentler in comparison to surface vessels because of its round hull and its low transverse metacentric height. The ship motion is dampened below the surface; below periscope depth there is almost no sensation of motion except in the presence of violent seas. An interesting phenomenon which has been described is the loss of "sea legs" during long submergence periods, and a greater incidence of motion sickness upon surfacing than before the dive. [color highlights added]

I have to take issue with both of Submarine Medecine's observations: ... [a] submarine's roll is believed to be gentler in comparison to surface vessels ... and never did I get seasick after prolonged submergence. Am I wrong? What are your own recollections?

Seasickness was a major problem in heavy seas before reaching the continental shelf. Afterwards, it was no longer a factor surface or submerged. On sea trials, for instance, the mess deck was awash in vomit. The odor alone would cause most of the people who had to come through either hatch to puke involuntarily. One of five in the control room watchstanders had barf bags at the ready.

After sea trials, most got their sea legs. Still, motionsickness in a rolling vessel with its log-shaped hull is the pits. Possible preventative: (this worked, and I can only guess it has something to do with the astronaut status mentioned in the first sentence) a few beers the night before always worked. Of course, this was not always possible.