Watch water resistance?

I recently got a new watch for my 18th birthday. On the back of it, it said "5 ATM". I looked it up, and supposedly it should be water resistant to 50 meters or 165 feet.
However, all places I went to online said to only have it around sinks, "slight splashes", shallow water, and to not use it for snorkeling.
I live near the ocean and would most likely use it for that; not for any real diving though.
Shouldn't a 50 meter tested watch be able to handle a few feet of water, or is it because it's saltwater that it would not be able to?

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If it's rated for 5ATM then it should be able to survive a 50 Meter dive. Is this a cheap watch or a nice watch? Really it doesn't matter. If it's a cheap watch and it doesn't survive a shower then you aren't out anything. If it's a nice watch and doesn't survive then the warranty should cover a replacement.

Salt water vs. fresh water doesn't matter. It's sealed to the point that it can handle 50 meter of water crushing in on it. Just don't try pressing any buttons while it's under water. Especially if it's a cheap one. Had a cheap watch rated for 100 meters. it was fine when i went swimming until one day i wanted to see the back light working under water and as soon as i hit the button the watch died. After a while with it out int he sun the moisture was cleaely visable on the screen.

The Dark Lord (author)  mpilchfamily3 years ago

Hmm...36 dollars, is that your "cheap", or no? It's a Neff Daily watch.

No a $30+ watch is a decent one IMHO. If it's a decent brand name (i.e. Timex, Casio, Armatron, ect.) i think you'll be fine.

I think you've done the math right.

It is funny how many different units get used for to measure pressure

http://en.wikipedia.org/wiki/Pressure#Units

Here are six different quantities approximately equal to one atmosphere, which is the absolute pressure of the Earth's atmosphere measured at sea level:

1 atm ~=

10 meters water ~=

32 feet water ~=

760 mm mercury = 760 mm Hg = 760 torr

100 kilopascals ~=

15 pounds/inch^2 = 15 PSI

So. Yeah. 5 atm ~= 5*(10 m water) = 50 m water, just like you already calculated. For anyone reading this who is used to pressure in PSI, 5 atm ~=5*15 PSI = 75 PSI.

So if the specification printed on the back of your watch were truthful, then yes it would be able to withstand being submerged to 50 m underwater, or maybe 40 m, if the spec is for absolute pressure, if we're counting the contribution from pressure of the "ocean of air", aka the atmosphere above, as well.

Also it should not mater if it is salt water, or pure water. It is not like salt water exerts more pressure than pure water. Also the seals on the watch are typically made out of some kind of elastomer that is chemically resistant to salt water. It is not like the seals are corroding under the influence of the salt water.

I think the real lesson here is that you just shouldn't put to much faith in advertising. I mean the people who designed the outside of your watch, they know more about fashion than they do about physics, and they want to put some numbers on the back of the watch that "look sexy".

In fact it may be the case, for the company that designed your watch, that the marketing people and the engineering people, do not even talk to each other, because these two groups think very differently, and their goals are often diametrically opposed.


GailP211 year ago

Salt water will kill your watch it is not recommended to wear in Sault water I killed mine in Sat water

I had a timex watch for about 3 years (rated for 50 meters), and one day I was on the beach and I forgot to remove it before entering the water (I always remove my watch before entering the water) and the next thing I saw was the watch completly dead (it was a digital one) just from some splashes from the waves, so, you shouldn't really believe the label.

After 3 years the little rubber gaskets inside where probably dired out and worthless anyway.

I believe this site may help you.

Watches which are water-resistant are tested for a single-time static pressure, which is in no way close to the conditions exposed during submersion/swimming/diving.

Water-resistant watches, no matter what ATM rating they have, are not meant for swimming/diving (although higher ratings can withstand such use).

What you want it a divers-rated watch.

Wikipedia also has a nice article about it.