Casio F91w at 5KM underwater – watches of espionage

Re:Casio F91w at 5KM underwater – watches of espionage by ndiddy on Friday January 31, 2025 @08:12AM (#42887306)

Was disappointed that he only brought a modified oil filled watch to 5km underwater. Would have been interesting if he’d have strapped a stock watch next to it so we could see when it would break.

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Re:Casio F91w at 5KM underwater – watches of espionage by rhd on Friday January 31, 2025 @08:37AM (#42887507)

This video might be of interest to you-

https://www.youtube.com/watch?v=iOT8XU1ss3E (Do Oil-Filled (Hydro Mod) Watches Actually Dive Deeper?)

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Re:Casio F91w at 5KM underwater – watches of espionage by homebrewer on Friday January 31, 2025 @09:37AM (#42888091)

A very similar model (A158 — they differ only in the bracelet) breaks at 200 m:

https://youtu.be/G3iMkeF8qmA

https://youtu.be/sep5Tw-55yw

The timekeeping mechanism keeps working fine, though, it's only the display that's busted.

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Re:Casio F91w at 5KM underwater – watches of espionage by dnisbet on Friday January 31, 2025 @11:01AM (#42888860)

Yep would have loved more on when the watch (unmodified) would actually break and also how you would fill it with oil? There can't be much space inside, at what point does the viscosity of the oil matter? how do you know you've got all the air out?

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Re:Casio F91w at 5KM underwater – watches of espionage by aidenn0 on Friday January 31, 2025 @11:23AM (#42889022)

I'm assuming they are using mineral oil; I've not filled a watch with mineral oil, but I have worked with it. Mineral oil is not particularly viscous; some gentle tapping is probably enough to get all the bubbles out.

Here's a video of a PC immersed in mineral oil with an aquarium bubbler and you can see the bubbles rise fairly quickly:

https://www.youtube.com/watch?v=tUBvWXH1hLs&t=110s

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