Warning about Garmin Descent!

[Nick_Radov]

Others have given you good feedback about how the device is working correctly. As a practical matter if you don't use Gauge then just remove that activity profile from the list. That way you can't start it accidentally.

 

[stiebs]

I had an interesting problem with my Garmin Descent Mk2i.... I went diving with it in the gauge mode - thus locking it in this mode for 24hrs. In this mode it only functions as a dumb depth gauge,

Hmm, let's take a look at the manual. Page 3:

It is a safety feature. In gauge mode the Mk2i, and every other computer out there (as far as I am aware) does not track your nitrogen loading. So if it allowed you to go back into a dive mode straight after a dive in gauge mode, it has no idea what you nitrogen loading is, meaning the algorithm does not have a known starting point and cannot be trusted.

No disrespect, but unfortunately you are the exact person that Garmin is protecting itself from. If you did an aggressive dive in gauge mode that pushed your nitrogen loading to the max, and then decided to switch it back to dive mode and did another dive with a 20 minute surface interface, the computer would probably give you a pretty long NDL because it thinks you started off with zero residual nitrogen. So you follow your computer and get bent, and then try and pin your medical expenses on Garmin (or your insurance does).

Much easier to just stop stupid people doing stupid things.

OK, maybe that was a little harsh. It's easier to stop people from overriding safety features that they don't fully understand, or don't fully understand the consequences of mitigating.

 

[johndiver999]

If you didn't want it to lock you out, then leave it in the gear bag for a day.. Simple as that. Don't keep diving with it in gage mode for multiple days and expect it to do something different after each day.

What else would you expect it to do?

 

[crofrog]

It would still be very unsafe to use the NDL from the Shearwater for at least 24 hours!
(unless your previous diving was minimal enough to leave very little nitrogen in your tissues)

Very unsafe is probably a bit of an exaggeration

A 20min dive to 100ft with a direct ascent to the surface at 25ft/min (can't use decimals in the time). The diver surfaces at a calculated 99% GF

Here is the second dive 12 hours later to 100ft for 20 minutes. Surface GF at the end of the dive is 99%

These are very aggressive profiles with no safety stops if you've added any conservatism in your planning the chance of it being an issue is pretty mute.

 

[stiebs]

Very unsafe is probably a bit of an exaggeration

A 20min dive to 100ft with a direct ascent to the surface at 25ft/min (can't use decimals in the time). The diver surfaces at a calculated 99% GF
View attachment 860745
Here is the second dive 12 hours later to 100ft for 20 minutes. Surface GF at the end of the dive is 99%
View attachment 860747

These are very aggressive profiles with no safety stops if you've added any conservatism in your planning the chance of it being an issue is pretty mute.

I wouldn't really call that an aggressive multi-dive profile. I'd actually say it's quite conservative. The first dive is within NDL, and a 12 hr surface interval is very conservative. The OP was on a dive trip, which quite likely could have been 3 or even 4 dives in a day. What if they did two 100ft dives in the morning with a 1hr surface interval, and this is their third dive for the day after a 2hr surface interval. NDL on that third dive would look very different.

The whole point is that when you put it in gauge mode, you have specifically told the computer not to track the gas that you're using or your nitrogen loading or oxygen exposure. So it errs on the side of caution.

 

[gschaut]

Sounds like an excellent opportunity to break out the tables, and calculate your no-deco limits manually. EVERY diver should know and practice using written tables. I dive with two computers AND a set of plastic tables in my fanny pack.

 

[johndiver999]

Sounds like an excellent opportunity to break out the tables, and calculate your no-deco limits manually. EVERY diver should know and practice using written tables. I dive with two computers AND a set of plastic tables in my fanny pack.

Fanny packs are so cool... especially for diving!

 

[Scared Silly]

Years ago we went off on vacation and IIRC one of our computers was still set for 1500 m rather than sea level. The second dive of the day ended with a serious but unnecessary deco obligation. Well that obligation was not going to get cleared so we did a normal safety stop. As advertised the computer said see you in 24 hours.

We said fine, computer you're on the boat. The next day we both followed the other computer with the diver sans computer staying above the other person. The third day we continued on.

Now would I recommend what we did to others. No. Simply because every dive scenario is different. The second days diving was "casual" for us so we were comfortable with our decision. We also dove conservatively. It worked and got around our mistake. YMMV

For the OP the old adage of "Good Judgment Comes with Experience, But Experience Comes from Bad Judgment." We got the same experience.

 

[Micko1974]

It is a safety feature to protect people from themselves.

Most problem are caused by human error.

 

[crofrog]

I wouldn't really call that an aggressive multi-dive profile. I'd actually say it's quite conservative. The first dive is within NDL, and a 12 hr surface interval is very conservative. The OP was on a dive trip, which quite likely could have been 3 or even 4 dives in a day. What if they did two 100ft dives in the morning with a 1hr surface interval, and this is their third dive for the day after a 2hr surface interval. NDL on that third dive would look very different.

The whole point is that when you put it in gauge mode, you have specifically told the computer not to track the gas that you're using or your nitrogen loading or oxygen exposure. So it errs on the side of caution.

The first dive has you surfacing at a gradient factor of 100%. That’s pretty aggressive, and the 12 hours is just to illuminate that a 24hr lockout might be a bit excessive