Diving during surface intervals?

[SeaHound]

I have a wreck dive at 100 feet. Right after that I have to observe of surface interval before making another dive to the same depth. What would happen if I choose to do a shallow dive to 25 feet BETWEEN the two dives?

Would I still be loosing nitrogen but degassing at a slower rate than I would be at the surface?

Would I be increasing NITROGEN levels in my body and therfore getting bends?

Thanks

 

[spectrum]

Different compartments would react differently. In some respects you would be off gassing and in other ways you would continue to saturate. The bottom line is that you need to manage the surface interval, however short for what it is. Planned right the 2nd dive to 100 will be delayed/shortened. It is a 3 dive outing, done by the numbers you won't get bent. There is no free lunch.

Pete

 

[ronbeau]

I have a wreck dive at 100 feet. Right after that I have to observe of surface interval before making another dive to the same depth. What would happen if I choose to do a shallow dive to 25 feet BETWEEN the two dives?

Would I still be loosing nitrogen but degassing at a slower rate than I would be at the surface?

Would I be increasing NITROGEN levels in my body and therefore getting bends?

Thanks

Also, remember that if the second dive starts within 10 minutes of the first 100 foot dive ending it is considered one continuous dive to 100 feet for the duration of the first dive plus the duration of the second dive.

 

[divenutny]

Seahound - IMHO, it would not be wise to skip your surface interval with a dive to 25 ft. Chart the dives, with the surface interval and without and see how the dive profiles are effected. I suspect the bottom time of the second dive to 100 ft would be dramatically shortened.

Good Luck - Tom

 

[LeadTurn_SD]

Seahound - IMHO, it would not be wise to skip your surface interval with a dive to 25 ft. Chart the dives, with the surface interval and without and see how the dive profiles are effected. I suspect the bottom time of the second dive to 100 ft would be dramatically shortened.

Good Luck - Tom

Agreed. Surface intervals are based on being on the surface. With two deep dives planned, I would not do anything to impair off-gassing during the interval between them.

Safe Diving!

 

[DandyDon]

And there is another problem. Take two warm beers - open one. No problem.

Shake the other a few times, then open it - big problem.

You don't want to do that with the micro bubbles in your body.

 

[DocVikingo]

It is a 3 dive outing, done by the numbers you won't get bent. There is no free lunch.Pete

Hi spectrum,

A slight modification, if I might.

Along with there being no free lunch, there are no absolute guarantees about not sustaining DCS. And especially not as regards the dives being entertained here, even when "done by the numbers."

Saying that, "It is a 3 dive outing. Doing your dives by the numbers reduces the chances of sustaining DCS to a very small probability" is more acurate.

Regards,

DocVikingo

 

[Dr Deco]

When you engage in this "surface interval dive," you are exercising and possibly could be forming tissue bubbles while you still have dissolved nitrogen in your body. This is not really a very good situation.:no

This question is similar to ones I received when this forum started in 2000.:11:

 

[UWSojourner]

The bottom line is nobody can provide you certainty ... not very satisfactory, but the truth. It would be better if you obtained an advanced rating so your excursion to 25ft was on 80% O2 or maybe up to 90%O2. Repetitve dives increase risk and jumping up and down the pressure gradient is generally not good. If you want to reserve the "right" to do these types of dives 1) get proper instruction to use better gases, and 2) do your research into decompression illness so that you know when you're "bending" the rules.

Otherwise, follow your instruction and don't break "the rules". Safe diving!

 

[lamont]

And there is another problem. Take two warm beers - open one. No problem.

Shake the other a few times, then open it - big problem.

You don't want to do that with the micro bubbles in your body.

And when you surface from the first dive you're going to have oversaturated tissues and you're going to have a bubble shower in your blood. Normally this is contained by the filter in your lungs. But if you do a bounce dive while you've got this free-phase bubble shower going on, you can compress bubbles enough to get them past the lungs filter and then re-expand them on ascent.

If you're going to do this, the second dive should be terminated by a period of real decompression... so spend much more time coming up (maybe 3ft/min) from the 25 foot dive... to use a similar analogy you need to slowly open the pop bottle, letting the pressure off gradually over a longer period of time in order to open it safely after it has been stirred up...

So, it can be done, but its not a good idea. And I have run into reports on this board of exactly this kind of behavior that has led to getting bent...

Also, don't free dive after scuba diving...