Nitrox course. What's the point?

[Storker]

depending on your dive profile, it may or may not make any significant difference to the plan

FTFY.

How do you determine your depth? Meter stick? Sure, then it may make a difference. Depth gauge/PDC? No way, because by default your gauge gives your depth in pressure, not as distance from the surface. No matter whether you dive mostly salt or fresh water (or whether that salt water is brackish water way in a fjord, or rather salty water at the coast), just keep your calibration at whatever you're used to use and follow your plan.

It doesn't matter whether you're 10 or 10.2 (or whatever else) physical meters below the surface. What matters is your ambient pressure. And given the large amount of uncertainty in our deco models, a 2% difference is truly insignificant even if it were real.

 

[Marie13]

10 mm wetsuit . Where do you dive? I love diving but cold would spoil my pleasure and dry suit make people look like astronauts without freedom of movements.

I dive the North American Great Lakes, with awesome wooden sailing ship wrecks more than 150 years old. Freshwater. It’s well worth dealing with temps colder than 45F/7C to see these wrecks. Warmest water I’ve had was 74F/23C at 60ft/18m. Too warm! I also dive a former mine in the region that has 50F/10C temps year round. I have more freedom of movement in my drysuit than a 7mm wetsuit. Fits much better, too.

 

[rick00001967]

FTFY.

How do you determine your depth? Meter stick? Sure, then it may make a difference. Depth gauge/PDC? No way, because by default your gauge gives your depth in pressure, not as distance from the surface. No matter whether you dive mostly salt or fresh water (or whether that salt water is brackish water way in a fjord, or rather salty water at the coast), just keep your calibration at whatever you're used to use and follow your plan.

It doesn't matter whether you're 10 or 10.2 (or whatever else) physical meters below the surface. What matters is your ambient pressure.

i completely agree and understand what you are saying. but that does not make the "theory" incorrect.

 

[Storker]

I think I look fine in my dry suit...

View attachment 635452 View attachment 635453

Is that guitar DIR-compliant?

 

[doctormike]

i completely agree and understand what you are saying. but that does not make the "theory" incorrect.

Actually, @Storker brings up a good point, and one that hadn't occurred to me before. Maybe I'm missing something, or don't know enough about dive science to realize the answer.

Why DO dive computers let you adjust for salt water or fresh water? Yes, there is a difference in density, but all deco calculations are based on actual measured ambient pressure, right? If you were diving in mercury or using it in a hot air balloon, wouldn't you want the DC to know what the depth was in ATA, not in feet or meters? And this implies that adjusting your DC for salt or fresh water introduces an error rather than corrects for one.

 

[doctormike]

Is that guitar DIR-compliant?

Not yet, gotta add a long strap.

 

[Bigbella]

I am not interested in deco or tech. I just want to be able to dive nitrox when it is possible or advised.

As an aside, nitrox use was also long-touted as being somehow "less fatiguing" than that of breathing conventional air; though, I have used it, off and on, since the early 1990s, when applicable, and have experienced no difference whatsoever -- that is, with the exception of a slightly lighter wallet . . .

 

[Storker]

Why DO dive computers let you adjust for salt water or fresh water?

Cater to the consumers.

all deco calculations are based on actual measured ambient pressure, right?

Bingo. 'nuff said.

 

[Storker]

As an aside, nitrox use was also long-touted as being somehow "less fatiguing" than that of conventional air; though, I have used it, off and on, since the early 1990s, when applicable, and have witnessed no difference . . .

Uh-oh. Yet another can of worms opened.

 

[rick00001967]

Actually, @Storker brings up a good point, and one that hadn't occurred to me before. Maybe I'm missing something, or don't know enough about dive science to realize the answer.

Why DO dive computers let you adjust for salt water or fresh water? Yes, there is a difference in density, but all deco calculations are based on actual measured ambient pressure, right? If you were diving in mercury or using it in a hot air balloon, wouldn't you want the DC to know what the depth was in ATA, not in feet or meters? And this implies that adjusting your DC for salt or fresh water introduces an error rather than corrects for one.

yes he is absolutely correct.

if we are diving fresh water and the gauge reads 34 feet, our depth gauge (being calibrated for sea water) "thinks" we are in 33 feet of sea water and so will read 33 feet. (10meters)
so in reality, we can do all calculations "as if" we were diving sea water.

my only point was that the actual manual arithmetic that we teach on a white board in class is different for sea water than it is for fresh. this should be obvious.

the practical difference in reality may not mean anything. A - we should never be diving that close to our limits anyway, and B - our gauges are most likely not that accurate.

btw.....this is a great conversation but may be confusing for some new divers. we should keep in mind this is the new divers forum. but i think the op has a good understanding of all that is being discussed. i love this s**t. thx guys !! always great to learn something new.