Descent Mk2i Locked to Gauge Mode

How so? 

nradov said:

What's the risk?

DCS, death, etc.

If it was just a single dive it would be no biggie, but the OP is on a diving holiday.  This likely means they will be doing multiple dives per day over multiple days.  Sure you could do it in dive mode but not only would it be an absolute pain working out each and every dive with tables, each dive would either be shorter or shallower and assume a square profile.

They've just spent a huge amount of money on a dive computer for a dive holiday and all they do is use it in gauge mode?  Sheesh!

Perhaps the best solution would be to leave the Mk2i out of the water for 24 hours and borrow another computer for that time.

But why the lock out at all? Makes no sense for guage

7000518 said:

But why the lock out at all? Makes no sense for guage

When you use gauge mode, it does not track tissue saturation at all. 

7000518 said:

Thats right, so why lock out? by definition its just measuring real time data with no calculations

It is not locking out from diving, just locking out from choosing a mode that will track tissue saturation.

Under normal circumstances you would start diving in say Single-Gas or Multiple-Gas Mode after not diving for some time. i.e. you have normal atmospheric tissue saturation.  The computer knows this and starts the calculations of tissue loading from that starting point.  For all subsequent dives, it will have a different starting point based on what happened for the previous dive plus the surface interval.

If you dived in the last 24 hours in gauge mode, the computer has no idea of your tissue saturation; none at all! You could have done a really deep dive with minimal deco and that would not leave you in the same position as if you hadn't dived at all.

What Garmin and other dive computer manufacturers don't tell you is that their algorithms have never been experimentally validated with a large population of divers for multiples dives per day over multiple days. There's no guarantee that the numbers on the screen bear any relation to what's actually happening in your body. I think many divers fail to understand the essential difference between precision versus accuracy, and thus have a false sense of confidence in what dive computers tell them.

In practical terms the risk of DCS for repetitive recreational dives is more dependent on individual physiology than the exact dive profile. I find it ironic when divers pay over $1000 for a dive computer, and yet have never even had a PFO test.

And death is not a realistic risk from using a dive computer in gauge mode. If you look at the DAN accident reports, divers almost never die from DCS. The real risks are things like running out of gas, entanglement, loss of buoyancy control, poor physical fitness, and incompetent boat captains.

This is a very good and often missed point that the original calculations were based on fit navy divers and extrapolated and as far as i know you cant get those numbers for yourself and set the conservatism parameters etc on that basis,

but the whole cut off of recreational diving depth around padi say was that in practice with non deco diving it doesnt matter because most risk is outside that if you stick to those rules,

As atj777 says you couldnt realistically emulate the accuracy of a dive computer through guage unless you dive restricted plans, the risk being exactly the unknowns you mention playing out viz gas narcosis or decompression sickness of whatever severity especially a few days into multiple dives because theres no point of reference, though in this case im sure hell be fine

Curious to know how guage was selected to start, wouldn't you have to set that or is there a default setting once you hit a certain depth?