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In a previous question, I established an area that creates megastorms.

Unlike a bunch of my other questions, this one is incredibly straightforward: Just how deep does a submarine (Or aquatic life, for that matter) have to dive in order to safely ignore a large-scale storm? It doesn't necessarily have to be completely calm, but low enough that the vessel could tolerate any issues that arise.

For reference, the technology level would be late WWII-era submarines.

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  • $\begingroup$ The question doesn't say but I assumed you were talking about open oceans. If you want to know about shallow water megastorms, then you'll need to clarify the question. $\endgroup$ – Green Jun 8 '17 at 21:52
  • $\begingroup$ Also, what's the wave height expected in this mega-storm of yours? $\endgroup$ – Green Jun 8 '17 at 22:20
  • $\begingroup$ With almost no knowledge of oceanography or meteorology, I couldn't even begin to guess what wave height would be like. Or how strong a storm would even be on my planet. Also, yes, figuring for deep/ocean waters. Shallow waters would result in Bad Things pretty much the whole way down, from what I can tell. $\endgroup$ – Andon Jun 9 '17 at 3:21
  • $\begingroup$ Is this a worldbuilding question, or just a question about the real world (meteorology, fluid dynamics, etc.)? If you're talking about a hypothetical, fictional non-Earth planet, about which you tell us nothing (gravity, atmospheric pressure, atmosphere and ocean chemistry, etc.), it seems like the only correct answer is “it depends”. $\endgroup$ – Peregrine Rook Dec 5 '17 at 23:49
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At least 400 ft deep.

A similar question was asked on reddit. To quote U235EU, who paraphrased the US Navy Submarine FAQ (now unavailable):

Violent storms may be felt as deep as 400 feet (see item 21). The deepest we ever felt surface effects was about 150 feet and it was pretty good sized storm on the surface above us.

That being said, multiple navymen on quora suggest otherwise, such as here and here.

Finally, The Huffington Post post covered What Happens Underwater During a Hurricane?

EDIT: The referenced Navy submarine FAQ was cached on the Internet Archive Wayback Machine! The full text reads:

During normal weather conditions, a submerged submarine will not rock with the motion of the waves on the surface. In fact, during even moderate storms the submarine stays perfectly level at its submerged depth while the waves crash above. In extremely violent storms like hurricanes and cyclones, wave motion can reach 400 feet or more below the surface. Though not as violent as on the surface, these large waves can cause a submarine to take 5 to 10 degree rolls.

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    $\begingroup$ So, 400ish feet to completely avoid things, but unpleasantly tolerable above that for the most part. $\endgroup$ – Andon Jun 8 '17 at 23:21
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    $\begingroup$ @Andon, on the Albaquerque at shallow depth under a storm, for entertainment, we would occasionally drop a No. 10 can (3 quarts, 6 pounds or so) of tomato soup unopened into a steam tray and lay it sideways on top of the steam line. If the storm swayed us just the wrong way back and forth, it could easily become an airborne missile capable of destroying a television and making the Chief Mess Specialist ask very pointy, epithet filled questions. $\endgroup$ – Sean Boddy Jun 9 '17 at 2:15
  • $\begingroup$ I fear that does not answer the question. The question is about safely ignorin - not about "not feeling anything". $\endgroup$ – TomTom Jun 9 '17 at 12:13
  • $\begingroup$ @SeanBoddy: great story! To understand what it implies for this question/answer, what exactly does “at shallow depth” mean there? Are we talking more like 30ft or 300ft? $\endgroup$ – Peter LeFanu Lumsdaine Jun 9 '17 at 12:37
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    $\begingroup$ @PeterLeFanuLumsdaine, due to a quirk of security clearance and the fact that I was actually there, I can't really answer that question. There's a lot of things I can carefully divulge about generic versions of specific systems when people ask, but position and depth I can't. There are some good guesses and outright exposures of what our periscope depth is, and I can allow you to guess that, on our way up to PD, we would stop at intermediate depths and make preparations. I will also say that PD in a big storm in the Albaquerque's hull sucked much worse than tomato soup missiles. $\endgroup$ – Sean Boddy Jun 9 '17 at 12:52
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I have been diving in Cuba right after a major hurricane (the hotel I was staying in was the only one reconstructed and active).

Devastation was to 15 meters.

No sign of damage below 20m.

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    $\begingroup$ It might be nice to have a picture or some other reference. $\endgroup$ – user25818 Jun 8 '17 at 21:32
  • $\begingroup$ @notstoreboughtdirt: I do not think I have underwater pictures. It was 2001 and I hadn't bought a serious waterproof camera at the time. I can surely dig some images of the destruction above-ground in La isla del la Juventud where I was staying. For generic info about the event see: en.wikipedia.org/wiki/Hurricane_Michelle $\endgroup$ – ZioByte Jun 8 '17 at 21:43
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Periscope Depth on the open ocean

Submarines in late WW2 were designed to handle overpressures of 20 bar (2.11169 MPa) at depths of 200 to 280 metres (660 to 920 feet). (Crush depths) Structures that strong can easily handle the pounding that a very large wave is going to dump on it. The humans inside the submarine won't like the jostling but the sub will survive. The shallow turbulence from the crashing waves is what the submariners feel at depth. The sub itself isn't in any danger.

Remember that submarines aren't designed with a hull shape that induces rotational stability like surface ships do.

Shallow waters are a different story

Because of the turbulence from very large waves from these megastorms, the waves may be large enough to force a sub to drop further in the water column than it should. If the ocean bottom is too close then the sub may crash. The exact effects will depend on ocean bottom composition, angle of impact, speed of impact and luck.

Shallow water during a storm would be dangerous to a WW2-era submarine.

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    $\begingroup$ Uniform compression and wave impacts are producing different kinds of stress. Glass sphere, for example, can withstand high level of pressure, but is very vulnerable to sharp impacts. $\endgroup$ – Alexander Jun 8 '17 at 22:04
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Not that deep. 50 meters should be enough to ride through a major hurricane.

https://www.reddit.com/r/askscience/comments/15b1jo/how_far_underwater_do_the_effects_of_a_storm/

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Category V S.S.S. with bottom plateau at 5K fathoms, experienced 2 degrees of roll until heading was changed by captain. Depth 560 ft. Then no appreciable movement was experienced. This according to chief bosun's mate. Cannot explain more detail.

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  • $\begingroup$ Cannot explain more detail? Please try. $\endgroup$ – Peregrine Rook Dec 5 '17 at 23:39

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