Doing the Deeper Dive Second.

[tville23682]

I have a dive partner who insists on doing the deeper dive second and a deeper diver if we do it a third time. He feels with longer Surface Interval Times that the depth of the dive and order doesnt matter. I strongly disagree with him and have successfully got my way each time we dive. I know i am cramping his style and our diving outings are becoming less frequent. How important is it so do the deepest dive first.

 

[Quarrior]

Not to be flippent, but, what do your tables tell you? Show them to your buddy.

 

[Gary D.]

I have a dive partner who insists on doing the deeper dive second and a deeper diver if we do it a third time. He feels with longer Surface Interval Times that the depth of the dive and order doesnt matter. I strongly disagree with him and have successfully got my way each time we dive. I know i am cramping his style and our diving outings are becoming less frequent. How important is it so do the deepest dive first.

It's safer by far.

One of the very few things that hasn't changed sense 62 when I started is do the deepest first.

If it's sport diving play by the rules. Sounds like he is cramping your style not you cramping his. Keep up the arugment and find another buddy.

Gary D.

 

[The Wanderer]

Give us some examples of the depth you are diving.

 

[ScubaDadMiami]

There are more than a few people that would agree with your friend. The reason has to do post dive bubbling/offgassing inasmuch as you are offgassing for some time after your earlier dive (depending on whom you ask, four hours to days).

By diving again, you are compressing the bubble just enough to allow it travel to potentially dangerous sites in the body (such as the Central Nervous System). When you surface, you now have a serious DCI hit.

By diving deeper than your first dive, you are much more likely to compress the bubble fully so that the inert gas is now back in solution (rather than just partially compressed as in the above statement). By carrying out proper decompression that accounts for the additional inert gas loading from the first dive which was shallower, you are theoretically safer than by diving the second dive shallower.

 

[murphdivers286]

Think about it this way; The whole dive industry teaches the dives after your first dive should be shallower. They based their teaching though years of professional research, along with trial and error from the past. I don't think all of the scientists through the years who have done extensive research to come up with todays teachings and tables could be wrong and your friend is right. (unless he is smarter than all of those scientists) I very much doubt it!!!!!!!!!!!!!!!!

I stick with what I was taught.

 

[CD_in_Chitown]

Then there are people like me who have always been taught the deepest dive first line from the agency but realized when I started reading up on it that there actually are schools of thought that say...

By diving deeper than your first dive, you are much more likely to compress the bubble fully so that the inert gas is now back in solution (rather than just partially compressed as in the above statement)

.........But don't get too worked up over whether we do the deep dive first or last just as long as we get to do a deep dive and we come up from every dive nice and slow.

I'm loathe to agree with Irvine but he has some convincing arguments for the deep dive last model.

 

[ScubaDadMiami]

The whole dive industry teaches the dives after your first dive should be shallower.

Not true anymore.

They based their teaching though years of professional research, along with trial and error from the past. I don't think all of the scientists through the years who have done extensive research to come up with todays teachings and tables could be wrong and your friend is right. (unless he is smarter than all of those scientists) I very much doubt it!!!!!!!!!!!!!!!!

Following this logic, we should all stick to the original tables put out by Haldane. What you might think is the latest thinking might actually be old news.

Things get updated and change over time. This is one of the changes. It is based on the scientific research you cite. Check it out.

 

[Coogeeman]

Yeah, everyone is telling you the same thing and you know what? everyone is right! Do your deepest dive first and then any consecutive dive has to be shallower. If your buddy doesn't agree get a new buddy but at least show him the dive tables first!

Coogeeman

 

[Kim]

There are more than a few people that would agree with your friend. The reason has to do post dive bubbling/offgassing inasmuch as you are offgassing for some time after your earlier dive (depending on whom you ask, four hours to days).

By diving again, you are compressing the bubble just enough to allow it travel to potentially dangerous sites in the body (such as the Central Nervous System). When you surface, you now have a serious DCI hit.

By diving deeper than your first dive, you are much more likely to compress the bubble fully so that the inert gas is now back in solution (rather than just partially compressed as in the above statement). By carrying out proper decompression that accounts for the additional inert gas loading from the first dive which was shallower, you are theoretically safer than by diving the second dive shallower.

I can see the reasoning in this - it in any event shows there is more than one view. I have a feeling though (only a guess as I've never done it - might try it later in simulation...) that my Suunto Vyper would be very unhappy with these sort of profiles and bottom times would shrink to very little. I'm not completely sure but I thought that the CMAS training also has something of this approach to bubble formation in it.