New Apple Watch is a dive computer

[Belzelbub]

NO MORE DECO DATA, just dive time and depth

This was in reference to going below 144'.

Ouch. In water lockout. Unless they are really not trusting the pressure sensor beyond 144' this seems like a very heavy handed approach. The algorithm is certainly capable of handling depths beyond this limit, though perhaps the app version can't.

I know it's probably not something most users will encounter, so probably not a huge problem. I'm just not a fan of lockouts in general, and really struggle to understand reasoning for an in-water lockout (hardware limitations aside).

 

[Eric802]

This was in reference to going below 144'.

Ouch. In water lockout. Unless they are really not trusting the pressure sensor beyond 144' this seems like a very heavy handed approach. The algorithm is certainly capable of handling depths beyond this limit, though perhaps the app version can't.

I know it's probably not something most users will encounter, so probably not a huge problem. I'm just not a fan of lockouts in general, and really struggle to understand reasoning for an in-water lockout (hardware limitations aside).

Time will tell - someone will develop an app that doesn't have the lock-out, and we'll see how deep the sensor can really work. I understand it has to have some limit, obviously, but having it "okay" at 40m and "dead" at 44m means they only designed in a 10% safety margin? Seems a little thin.

 

[brsnow]

I guess the question would how many recreational divers go to 144 feet.

 

[Hoag]

I guess the question would how many recreational divers go to 144 feet.

I am very much a recreational diver and I have been below 144ft but only once. I was at about 125ft in the Great Blue Hole in Belize when one person in our group started to stare intently (and intensely) at their computer and then dropped like a rock. Two of us went after her and caught her at about 140ft, and by the time we had her descent stopped, we bottomed out at 149ft before we were able to get her to start ascending up to where the rest of the group was. We were at 149ft for only a couple seconds, but we did get there and I would have hated if my computer would have locked me out for 48 hours after that.

 

[Belzelbub]

I guess the question would how many recreational divers go to 144 feet.

Undoubtedly, it's a small number. However, to do an in-water lockout seems extreme. The in-water lockout is basically the computer telling the diver to "F off" you are on your own. I can only really think of a few reasons to do that.

1. Hardware limitation of the software. Seems unlikely, but I guess possible. In this case, the sensor is determined not to be accurate at that depth, so using the inputs of the sensor for calculating tissue loading is probably not going to work to well.
2. Space limitation for the app. Oceanic didn't have the space to implement the full algorithm, so they cut it at 144'. I don't think cutting at 144' is going to save a ton of storage space, so I don't think this is likely either.
3. A business decision to clearly not advise going beyond 130', and penalize strongly if continued. Oceanic's other computers don't do this to my knowledge. While this seems most likely, it still seems odd.

I am very much a recreational diver and I have been below 144ft but only once. I was at about 125ft in the Great Blue Hole in Belize when one person in our group started to stare intently (and intensely) at their computer and then dropped like a rock. Two of us went after her and caught her at about 140ft, and by the time we had her descent stopped, we bottomed out at 149ft before we were able to get her to start ascending up to where the rest of the group was. We were at 149ft for only a couple seconds, but we did get there and I would have hated if my computer would have locked me out for 48 hours after that.

Thanks for posting this. While it shouldn't happen, it does happen. What's even worse, though is what would have happened had you been diving an AW Ultra with Oceanic+. You would lose your depth once you descended below 130'. Then, in the case here where the bottom was at 149', you wouldn't know you reached this depth. Even worse, once you got control and ascended above 130', your depth would display, but you would find that you wouldn't have any decompression recommendations on the computer. It would just give you time and depth. That's got to be a bit disconcerting knowing you went off plan, went pretty deep, and have no idea, if you've exceeded NDL, or what stops you need during ascent.

 

[brsnow]

Undoubtedly, it's a small number. However, to do an in-water lockout seems extreme. The in-water lockout is basically the computer telling the diver to "F off" you are on your own. I can only really think of a few reasons to do that.

1. Hardware limitation of the software. Seems unlikely, but I guess possible. In this case, the sensor is determined not to be accurate at that depth, so using the inputs of the sensor for calculating tissue loading is probably not going to work to well.
2. Space limitation for the app. Oceanic didn't have the space to implement the full algorithm, so they cut it at 144'. I don't think cutting at 144' is going to save a ton of storage space, so I don't think this is likely either.
3. A business decision to clearly not advise going beyond 130', and penalize strongly if continued. Oceanic's other computers don't do this to my knowledge. While this seems most likely, it still seems odd.

Thanks for posting this. While it shouldn't happen, it does happen. What's even worse, though is what would have happened had you been diving an AW Ultra with Oceanic+. You would lose your depth once you descended below 130'. Then, in the case here where the bottom was at 149', you wouldn't know you reached this depth. Even worse, once you got control and ascended above 130', your depth would display, but you would find that you wouldn't have any decompression recommendations on the computer. It would just give you time and depth. That's got to be a bit disconcerting knowing you went off plan, went pretty deep, and have no idea, if you've exceeded NDL, or what stops you need during ascent.

If it is a company decision based on liability, would be interesting to see if these types of restrictions spread to other computer makers. Especially with insurance cost in the industry rising. The amount of forms and medical consents for dive trips that were previously never asked for. There seems to be a shift to more regulation.

 

[scubadada]

If it is a company decision based on liability, would be interesting to see if these types of restrictions spread to other computer makers. Especially with insurance cost in the industry rising. The amount of forms and medical consents for dive trips that were previously never asked for. There seems to be a shift to more regulation.

My family and I have been diving Oceanic computers since 2002, Pro Plus 2, VT3, Geo2, VT4. No Oceanic computer has a relatively shallow depth limit like Oceanic+. I have no fear that Oceanic or other dive computer brands will introduce a depth limit similar to that in Oceanic+.

I wish I understood why Oceanic+ has this limit. As I can't imagine why Oceanic would request it, I can only think that it is an Apple specification, hardware limit or philosophical decision. Perhaps we will know the answer at some point.

 

[Ryebrye]

Undoubtedly, it's a small number. However, to do an in-water lockout seems extreme. The in-water lockout is basically the computer telling the diver to "F off" you are on your own. I can only really think of a few reasons to do that.

1. Hardware limitation of the software. Seems unlikely, but I guess possible. In this case, the sensor is determined not to be accurate at that depth, so using the inputs of the sensor for calculating tissue loading is probably not going to work to well.

Well... maybe... but it seems like they could make a better guess unless the sensor itself maxes out it's reading at that point. 144 fsw is around 5400 mbars. Maybe Apple caps the sensor output to 5400 mbars for some arbitrary reason?

But what doesn't make sense is that they say it continues to show "time and depth" if you are beyond 144 ft? If the pressure sensor can tell you your depth, you have all the info you need to calculate the tissue loading.

Maybe they mean it will show you the time and depth when you go back above 144ft?

2. Space limitation for the app. Oceanic didn't have the space to implement the full algorithm, so they cut it at 144'. I don't think cutting at 144' is going to save a ton of storage space, so I don't think this is likely either.

The Buhlman algorithm does not require anything extra to handle deeper depths. It's based on tissue loading of the compartments based on the ambient pressure. There's no code space benefit from having it cap it there.

 

[L13]

1. Hardware limitation of the software. Seems unlikely, but I guess possible. In this case, the sensor is determined not to be accurate at that depth, so using the inputs of the sensor for calculating tissue loading is probably not going to work to well.

I don't think this is actually unlikely. In fact, I think it is the most likely reason.

If the sensor is in fact likely to be unreliable below 44 meters, any nitrogen calculation after that would be suspect regardless of depth, and they would not want to be liable for any actions based nitrogen reports. Given the type of MEMS sensors likely used, it is likely that the depth measurement would be good again once you returned to its operating range. So continuing to display the usable data (time and depth) while not displaying anything nitrogen related, since it would be erroneous, makes sense. A 48 hour period at 1 ATM also makes sense to wash out enough of the nitrogen for the calculations to be relatively certain that the calculations are fairly accurate (~4-5 half lives for the slowest tissues).

There are a number of MEMS sensors on the market with a reasonable form factor for this use with a max pressure range of 5 ATM absolute, which is about 40 meters (44 meters with the likely 10% margin on the spec).

I suspect the limit is mostly driven by sensor selection.

 

[drrich2]

I wish I understood why Oceanic+ has this limit. As I can't imagine why Oceanic would request it, I can only think that it is an Apple specification, hardware limit or philosophical decision. Perhaps we will know the answer at some point.

Combining the 48-hour lockout with the 'you must affirm readiness to dive before every dive' silliness, my 'read between the lines' impression is that Oceanic believes their target customer demographic for this product includes a lot of newbie or 'dabbler' occasional vacation divers who are marginal and ought to be treated with a higher-than-usual level of 'Big Brother' coddling. Perhaps they think many Ultra owners will be inspired to try scuba diving because their gadget can support it (and a few of them might die, leading to potential lawsuits)? Or that more dedicated divers either have or will likely get a more 'dedicated' dive computer?

Speculation, but a company's approach says something about what they think of their perceived customer base.

Richard.