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Comment by ashtonbaker | Hacker News Reader

I think this looks amazing for warm-water vacation divers - typically they are stuck with rental equipment, which usually means a cheap, dated computer on a bulky console. Having a well-designed UI will definitely improve these divers safety - the last boat dive I went on, an experienced diver blew past no-deco limits because he didn't understand his unfamiliar rental computer.

That being said, I can't personally imagine taking the Apple Watch Ultra to, say, 80-90 feet if it's only rated to 130. It's just too expensive.

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Slight clarification: the Apple Watch Ultra has a water resistance rating of 100m. The Oceanic+ app has a 130ft/40m limit because that's the recreational diving limit.

[1]: https://support.apple.com/kb/SP879?viewlocale=en_IN&locale=e....

Oh, cool! It looks like that's the limit of Apple's Depth app, as well, which is what I found when I searched, and assumed it was the limit of the watch.

Well that's definitely better - I wonder what happens when you go under 130 feet, though. A dedicated dive computer would at least provide accurate information, rather than throwing you to the wolves because you exceeded some legal limit.

Also on the plus side, some of the existing air pressure transmitters use bluetooth, so if they could get that working, they'd actually be one of the cheapest air-integrated computers on the market.

(edit: they do not use bluetooth, they use low-frequency radio ~38khz)

I think I'll stick with my Shearwater Peregrine though, pros and cons considered.

I like that you assume it's going to shit the bed vs. assuming that they planned for it, given the hardware supports it.

I'm not assuming anything - and I'm not speaking as a pundit on Apple, I'm speaking as a consumer in the target audience with specific, important questions about a safety-critical piece of equipment. The answer to my question is not clear from this marketing release, and I'm simply saying that affects my likelihood to purchase.

Also, in the case of lack of evidence either way, assuming it would shit the bed is _definitely_ the right approach in diving.

It's human instinct to survive time will tell if this new thing is comparable to a real dedicated diving computer. Diving is dangerous.

Knowing the current state of software development and Apple's tendency to make pretty things on surface but that breaks down when you actually use it, I'd expect it to tell you you can swim as fast as possible to the surface without decompressing, even from 100m deep.

DC Rainmaker showed what happens to the watch when you take it past the max depth in his review [1] (using a pressure chamber).

I think your concerns are valid and merited for your very advanced level of diving, but at the same time the vast, vast, vast majority of divers aren't going anywhere near 130 feet. If I were going on a standard "simple" dive to <60 feet, I think I'd be pretty comfortable with just the apple watch ultra, a dumb watch + cheap depth guage and a written back-up plan.

1: https://www.dcrainmaker.com/2022/11/diving-with-the-apple-wa...

Yes, agree completely. Would be happy to have just this on a 60 foot dive. And will be happy to see it on the wrists of other divers on the boat, as I think it will make them safer vs the status quo. Just wouldn't _buy_ it for that purpose myself, I think there are better options if you research a bit.

Also, I never dive past recreational limits, I'm not a technical diver by any means. I would simply have philosophical concerns about a piece of equipment that could provide accurate information beyond recreational limits, but simply doesn't for "legal" reasons. It probably makes sense to people - "oh they don't want to be liable for giving advice past recreational limits", but other companies seem to have navigated this legal issue and choose to provide accurate information regardless of this arbitrary limit.

As another commenter pointed out, I have no idea what it does past 130 feet, but the disclaimer that it _cannot_ be used past 130 feet, rather than one that says you _shouldn't_ use it past 130 feet, is somewhat concerning to me, even if I don't approach those limits.

For those curious, 40m is a standard cutoff for rec diving because

A) oxygen partial pressure with compressed air reaches 1.05atm, with 1.2-1.4atm posing a serious risk of oxygen-induced seizures (extremely dangerous)

B) nitrogen partial pressure becomes high enough that it becomes narcotic (every gas gets you high at enough pressure, even noble gasses).

There is virtually zero risk of an oxygen toxicity seizure in the 1.2 - 1.4 atm range. I don't think there has ever been a confirmed case of a sport diver toxing at that level. We normally target about 1.2 atm for the working phase of the dive (reduce slightly for long exposures) and 1.6 for deco (with back gas breaks for long oxygen stops).

Narcosis is an issue with nitrogen and oxygen (as well as most other gasses). Helium is the exception. It is a noble gas and has no real narcotic effect; rather the opposite. Other noble gasses such as argon are much more narcotic than nitrogen and aren't used as diving breathing gasses (outside of a few limited experiments).

The other problem with nitrogen and oxygen is that they are relatively dense and so at greater depths they cause increased work of breathing, which in turn causes CO2 accumulation. CO2 is itself highly narcotic, and has other negative physiological effects. So for deeper dives we add progressively more helium to the mix.

I took it to 140ft a month ago. It complained and turned the screen yellow as a warning, but readings in the built in Depth app (which measures depth, water temp, and dive time but is NOT a dive computer) matched my dive computer exactly at that depth and all other depths.

It’s rated as water resistant to 100m, 300+ feet - it’s just the software and measurement sensor bits that get queasy at 130ft.

The software APIs for measuring depth have an enum for this: https://developer.apple.com/documentation/coremotion/cmwater...

Was curious about this myself. I've gone deeper than 40m on a recreational dive, blue hole I think. Obviously they aren't 'supposed' to do that, but it obviously routinely happens and it'd be a bummer if your fancy watch dies at that depth

> That being said, I can't personally imagine taking the Apple Watch Ultra to, say, 80-90 feet if it's only rated to 130. It's just too expensive.

I get the feeling of it being too expensive - but technically? If anything is to be expected from Apple, it is to under-promise on advertised specifications, and at least here in Europe, under consumer protection laws I can hold Apple accountable for not delivering upon their spec [1]. The hardest thing with anything underwater is pressure differential anyway - old analog watches have a lot of air inside which is compressible, which means you need strong seals and construction to avoid the pressure differential to simply crack the case. A modern digital watch however? Space is scarce so every cubic millimetre is packed with solid incompressible materials, making it way easier to withstand higher pressure.

[1] Actually had to do that with a CAT phone many years back when I worked in construction, a simple fall on a floor slab broke the screen. I made a backup (back then, that was actually feasible because rooting was easy, another personal gripe I have with recent Android), went up to the retailer and had it shipped in - a week later I had a brand new device and a written apology that the product was not up to spec.

My understanding is the Apple Watch Ultra is physically rated to 100 meters / 328 feet.

The 40 meters / 130 feet rating is for the dive computer functionality.

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