In one of the scenes in Das Bootthe submarine goes through a fierce storm which becomes stronger and stronger. At one point the captain decides to submerge the boat because floating through the giant waves was no longer save.
So the boat dives and after a short period of time everything is quite, calm and peaceful aboard the submarine. The submarine remains submerged for many hours and sits out the storm. It is later revealed that a number of ships indeed fell victim to the storm and sank. The captain of the submarine says (words to that effect): Submarines are the most seaworthy ships that exist.
How deep must a submarine dive to completely avoid a force 12 storm?
Not very deep - surface storms are destructive to boats due to winds and the turbulent interface between air and dense water. Once you are submerged deep enough to stay submerged, there is still some turbulence, but not the interfaces between air and water that affect stability and structure. These drop off with additional depth. Past about 100m and you are through the thermocline, and surface turbulence has almost no impact on water mixing.
I don’t have an exact answer but I recently watched a documentary about the 2004 tsunami where several survivors were interviewed. One family was SCUBA diving when the tsunami occurred. They mentioned that the “currents” were crazy and it was a very tough dive. Of course, thousands on shore were dying during that time. Point being, if submerged humans are minimally affected by the surge from a tsunami, I don’t think a sub has to go very deep to avoid a surface storm.
I kind of doubt a sub would even need to get to 100 meters.
Based on my personal experiments at the beach as a kid, when it was really choppy and there were fairly big waves, you didn’t have to go very deep at all to not have the water moving at all.
(this is assuming you’re out far enough that interaction between the waves & the bottom is not an issue).
I remember once reading about early U.S. Navy submariners c. the 1920s. They couldn’t go very deep at all (don’t recall what was their max depth), and even when submerged suffered from terrible buffeting during storms.
IIRC, Das Boot features a Type VII (not sure which variant), which according to Wiki has a max depth of 220 meters. So weathering the storm should have been no problem at all.
It also depends on whether there’s anything to bump into. Being moved around by the waves underwater would be far less damaging than on the surface. For example, the Edmund Fitzgerald sunk because its ends were on different waves, spanning the trough between them. Freighters aren’t designed to support themselves that way. Capsizing is also far more likely. Underwater, I bet you can withstand considerable motion without severe damage. Unless you hit something, that is.
I remember scuba diving off Aitutaki in the Cook Islands. The divemaster cautioned the four of us to stay put and stay together as we descended, and to wait for him to guide us. We found out why. After descent, we stayed together as a group, as the ground passed below us, first one way and then the other. Turns out there were big wave (albeit shallow ones, barely noticeable on the surface), and we desceneded just outside a break in the barrier reef. As the water flowed in and out of the passage, we zoomed back and forth. However, we couldn’t sense our own motion and it seemed like the world was whizzing by. The divemaster timed our exit, and we calmly swam along the barrier dropoff.
This post wins an award of some kind! I can only imagine being seasick and without even the possibility of going topside. But, I’d rather not, thank you.
Get the average height of the waves that form (trough to crest) and draw a circle with the center maybe 1/3 of the height below the base of a wave and the circumference touching the crest. The water particles will oscillate along that circle in cross-section. There will still be disturbance below that circle but will be progressively weaker as you go deeper. It’s a progression of circles whose diameters shrink as you go deeper.
I rode out a “perfect storm”-type storm in a submarine years ago. It wasn’t really noticeable at depth, except that the sonarmen kept complaining about all of the noise on the surface. Based on the sound, the sea state was estimated to be 8 or 9.
We were scheduled to go to periscope depth at one point during the storm. At about 200 feet (during our ascent), we were already doing pretty severe rolls, so we gave up and went back down to ride out the storm.
I think the fish were sensible enough to stay out of the channel. But of course they would have been, just as a seagull is affected by the wind. I assume most of us have seen a seagull flying upwind but not fast enough, consequently going the opposite way. (Not for long, of course, they’re better evolved than to waste much energy doing that.)
I’m really glad the divemaster showed us that. I’d estimate that we moved over 50 feet from innermost to outermost. It seemed like even more than that, so I’m trying to be conservative. The bottom was about 10’ below us. I still remember the astonishment I thought I could see on the faces of the other guys – usually one can’t see any expressions with mask and regulator in the face. I bet I looked the same way. It was a long time ago now, but I’d say the oscillation period was in the 5 to 10 second range.
I happened to be facing away from the atoll, so I didn’t really see the barrier wall rush at us and fade away. Just the ground below us. I was very new to diving then and didn’t want to get separated from the others, so I didn’t turn around to look. I wish I had. But I could tell what was going on.
Certainly in the shallows divers can be pushed around quite dramatically. I remember a dive in St Barths were we swooped back and forth across the reef as waves passed, easily oscillating 50ft.
At 18m (60ft) the soft corals can be swaying as waves pass overhead. Drop down below 40m (130ft) and there is no noticeable movement due to overhead waves of 3-4m though there may still be currents in the area.
A while back, I asked a question about how a submarine would be affected by a tsunami, which is essentially a massive, fast moving current. I remember getting some equivocal answers that pretty much said “I dunno”.
The latter. I think we were doing 15-20 degree rolls, which is a lot at that depth.
Roll is defined as the “rotation of a vessel about its longitudinal (front/back) axis.” It doesn’t necessarily mean that the vessel rolled completely over (i.e. capsized). That would be catastrophic for a submarine, whether surfaced or submerged.
A tsunami is not a massive, fast moving current. A tsunami is a fast-moving (hundreds of miles per hour) wave that in the open ocean has a very long wavelength (hundreds of miles), but a relatively short amplitude (one meter or so). Out in the open ocean, ships (and submarines) likely would not even notice the wave because of the short amplitude.
What’s remarkable about a tsunami is that because it’s caused by a large underwater displacement, such as an underwater earthquake or landslide, the wave affects the entire water column (not just the top few meters, as in surface waves caused by wind).
You only notice the difference in the waves when the tsunami approaches shallow water. In shallow water, the wavelength of a tsunami decreases by an order of magnitude or so, while the amplitude increases dramatically.
So anyway, a submarine at sea would likely not notice a tsunami any more than any other vessel at sea.
