Is 50 meters water resistance too risky?

...because you don't understand neither the physics, nor the maths.

That's it. I'm not trying to be rude or unpolite; I'm just stating a fact: you think your hypothese holds water (pun intended) because you just lack basic understanding on what's happening.

I don't know where are you from, but I'm fairly convinced that within the obligatory education period on any... well, anywhere, the notion is taught that while gasses are compressible (maybe the expression "Boyle-Mariotte Law" can even ring some vague bell in your memories), liquids are not. You may not remember, or even learned, exactly why, but at least the concept itself should be known, so there it goes your "principle" about mollecules themselves compressed through a crack (of course, that liquids are imcompressible is, as basically everything at elementary level, a valid-enough aproximation for lack of further knowledge about the petty/pesky details but still, valid-enough for the general case).

With further specialization (but even then, still not university-grade), you'd remember about Van der Vaals forces that offer explanation on why solids/liquid/gasses tend to behave the way they do; you'd know that solid/liquid/gas is not the everything about states of matter, or you'd know about what the four basic forces are and how they interact (or do not interact) to shape our physical universe.

All in all, you'd know that, as others already told you, you shouldn't look for quantum mechanics to find explanations on why water enters -or doesn't enter, into a wristwatch but that the proper place to start your information is very likely, that Bernoulli nice guy's work, or maybe Navier and Stokes -which, alas, you decided to ignore.

Even without the knowledge, you should know, just by living in this world, that even if you don't know the right answer, the answer must be known since, for instance, you know, if only from filmes and TV news, there exist those thingies, "submarines", that, more often than not, not only go deep into water, but also come back to surface unscathered. That means the why and why nots of how water enters closed receptacles must be well known by now and it also means that engineers, which are the graduates that deal with designing those thingies, should be knowledgeable on those why and why nots. So when someone tells you he's an engineer (up to the point you believe he's not lying) and you are wrong in your engineer-related believings, you'd better believe him (authority argument is Popper's weakest one, but it's still an argument), and when he tells you "if you are interested in theses issues you should look at this and that", you either tell to yourself "OK, I'll do the effort" or "No, I don't think I'll do the effort, so my default possition should move to 'he's right, I'm wrong' because of his authority in these issues".

No: even in democracy, your ignorance is not as valid as his expertise.

Well, be happy then, knowing that you already live in such a world.

It's only the rating you are looking for is not the one associated to "water resistance" (ISO-2281) but the one about "diver's" (ISO-6425).

And even talking about "water resistant" watches, its legal notion is one of minimals, being up to the vendor how much does it back it claims. Given this, I'm fairly confident a, say, 50m Omega can withstand 50m worth of water on top, but I most possibly wouldn't have a shower with a Parnis dress watch rated [basically whatever].

You wouldn't be saying "space is everywhere" if you lived in my first flat 😉

This is the main point here, I think. These things are not easy to grasp and many people think that after a few hours on Google/YouTube they have some understanding of one of the many fields of science. We shouldn't be too critical as it seems that the majority of people think this.

The pandemic is an issue where everyone is frantically reading a few documents about vaccine "efficiency", as I read on another thread, and deciding they can then make decisions based on that. Very few people are qualified to make decisions or form opinions in these matters so, it tends to be just well meaning noise.

All these discussions are interesting but it seems to me that if the manufacturer says 50m then don't overthink it - you're fine to 50m.

In terms of pressure and structural resistance, I often quote that the typical aluminium skin thickness of a commercial airliner, away from cutouts, is 0.050" (1.25 mm) and so, I don't worry about thick steel diver's watch cases...

Regards, Chris

Hi Dan

I was trying to make a point that things are not so easy to understand but, appreciate you mentioning this.

Civil airliners are designed (typically) for a pressure differential of approximately 9 psi but, we put a safety factor of 2 on that so, 18 psi or about 1.25 atmospheric pressure. We don't worry too much about impacts or tread loads but, it's virtually all about strength and for watch cases, it would be virtually all about deflection - so, my point is not perfectly made. Wings and the like do have a tread issue.

Hoop stresses due to internal pressure are related directly to internal diameter (a lot bigger in an aircraft, obviously) and inversely to wall thickness, a lot smaller as we typically use 0.050". We also limit stress due to the nature of aluminium which doesn't have a fatigue threshold like steel. My point (badly made) was that many things we think we understand are not so easy to grasp and people are often surprised when I mention how thin a fuselage is.

Of course, we worry about losing the aircraft (and many people) so, it's a bit more critical but, as a watchmaker (I have stopped with aircraft engineering), we don't want to see watches with water inside either. I suspect you and I are of the same opinion here about water resistance.

Did I mention that the pub gardens are open in England and I was dragged into one earlier so my posts may not be as clear as I'd like😁

Cheers, Chris

So that's why my only dress watch is a Seamaster. My subconscious must have been thinking about the Charles River (and later River Cam) when I bought it.

Ok, apologies if i upset anyone, i'll not bother you anymore with gibberish, it's the only way i know to prove i'm not a troll, i.e. someone who's out to ruin a conversation just for fun, have a good day all, no hard feelings i hope, i certainly didn't intend any.

I don't think that's the main point.

On one side, I'd say that the Universe is quite a strange thing and that our understanding (as Humankind) of it is quite advanced nowadays is an output everybody can get out of obligatory school (that means it's open to anyone about 16 y.o. or over). Moreso, if your pass through obligatory school was less than stelar.

I can even get that "few hours of Google" can give us sometimes a false sense of understanding (but here we are already entering Dunning-Kruger territory -if our world is quite a complex thing, how is it those guys seem to have simple solutions to complex problems? How is it they are airing them in YouTube instead of Academia?).

What I can't understand, and I can't accept, is that the false sense of understanding stands against the very first dialectic encounter: "this guy says he's been studying the issue years after years but, hey, I know better because I've seen some random videos on YouTube". That's not only weird, but it comes as a (relative, starting from like the 70's or so) novelty against the usual standard of "I'm a peasant and he's a wise man: he knows better" (so much was so it could also be abused too).

I said the 70's since I think this Asimov's quote comes from the early 80's (and certainly I think Reagan/Tatcher rise to power acts as a milepost signing that change) -he talked about USA, since it's where he lived, but I'd say it spread everywhere: “There is a cult of ignorance in the United States, and there has always been. The strain of anti-intellectualism has been a constant thread winding its way through our political and cultural life, nurtured by the false notion that democracy means that 'my ignorance is just as good as your knowledge'.”

It seems he was right since it neatly explains terraplanism, antivaccinism, 5G blood-chips, and some other more dangerous things.

here we go again

While every ones entitled to an opinion, they are not entitled to that opinion being right.