Free Diving same day as Scuba?!

[dvoodoo83]

thanks for that link pipedope thatexplanes a lot

 

[divebunnie]

Yeah, I too did not learn this at open water stage, and only found out once I started talking about things with fellow divers.

Of course, now I think about it, it is logical, if you recompress the excess nitrogen and shoot back to the surface, there is the absolute chance that it can form bubbles. But it does seem to be one of those things that you find out about later on… all good reason to include it in the OW. I know the skin dive is optional, so maybe most instructors point this out at that stage, I am not sure.
It's certainly a valid point to make, and more people should be aware of the potential risk.

 

[DandyDon]

Hey, lots of response here - THANKS! Something of a summary...

I don't recall anything either and I just finished my OW training a few months ago. Guess I should take a looksee.

I don't think that the agency courses are calling for this, even though some instructors are including it. Guess you can't cover everything but - dang! I remember planning my first dive trip, thinking: "Well, if I can't dive for 24 hours before flying, I guess I can freedive?" Glad I didn't! Now, DAN has dropped the wait time to 18 hours, and it takes me that long to dry & pack gear.

I actually just got back from a spring break trip with my instructor. He not only encouraged, but participated in snorkeling and spearfishing after 2 morning dives. The spearfishing took us to at least 20 feet, but he didn't seem to be concerned. I trust him, as he has over 2000 dives. I wasn't even aware that there was a snorkeling limitation after a couple of dives.

This is scary. Christopher, how about running Pipedope's link http://www.wkpp.org/articles/Decompression/why_we_do_not_bounce_dive_after_diving.htm
by your instructor, and let us know what he says - or better yet, ask him to come on here...??

The real concern would be repeated freedives with fast ascents after already built up a significant nitrogen load. I know of at least one person who developed a pretty good case of Decompression sickness due to freediving after scuba dives. Some bubbling of nitrogen, although not enough to be symptomatic, can be there after dives. Repeated free dives with associated rapid ascents will force these bubbles back into solution and out again causing them to grow. Many have been known to get away with it, but why take a chance?

Exactly!! And with your credentials, who could argue...?!

Did I miss something?

Why did you call DAN over a few 15' free dives conversation over lunch? Did he have a headache already?

........

When in doubt make the call. Better safe than sorry.

Yeah, 15 feet wasn't much, but still - I wanted to play it safe. So I called someone who knew more than me - DAN. My bud, still kinda' new, didn't know that you can just call them 24/7; I'm glad he got that out of the experience. Membership not required, although I think a good idea.

this topic was covered in my OW, as a big no-no.

i was told severall times not to do it and the topic was even debated when we were on the boat because one of the divemasters on board was telling a story about an instructor who had died a month or so before, with shallow water blackout, diving alone.

Shallow Water Blackout is another risk associated with Freediving, but not related directly to this, I don't think.

Read this;
http://www.wkpp.org/articles/Decompression/why_we_do_not_bounce_dive_after_diving.htm

All of the people I have known who had a bad DCI hit had done a bounce dive or free dive after a deep dive.

I always expect good input from PIPEDOPE! THANKS!

 

[Bob3]

It's those darn bounce dives that'll get ya, just another good reason not to load yourself up right to the ragged edge of the NDLs.
A DCI hit isn't a matter of black & white, it's a gradual thing.
More folks have been bent & not realized it than what you'd like to think about.

 

[divebunnie]

Must admit, I have yet to discover the joys of bounce dives.
I am about to do my Divemaster course in Sharm el Sheikh, and the one thing that is a little concern is the bounce dives that the guides have to do to moor off on the Thistlegorm, never popular, and by all accounts, sound a little risky.
Any hints?

 

[Walter]

Most OW classes don't teach skin diving. Why would they cover this?

From what I understand, it's only recently that this was discovered to be a problem at all. I know I used to do lots of free diving after SCUBA dives. I never had a problem. OTOH, I'm pretty careful about it now.

I can't imagine 15 ft would cause a problem.

 

[CBulla]

There isn't much of a concern at all about free diving and that sort of activity. First off your not going deep enought on gas at 15-20'. Second, the air you have is that you put in your lungs at the surface, not whats in a tank that your breathing from, so there isnt any expanding gas issues. Even with built up nitrogen from earlier diving, there should be no concern.

I asked DrD back in October about shallow dives in this thread, to which I think there is applicable information for free diving as well: http://scubaboard.com/t39880.html

 

[MSP Rescue Diver]

I just posted and referenced this thread to Doc Deco in his forum to see what he says.

I vaugely remember reading something that nitrogen loading is not an issue for free divers as they are diving on one breath and are not breathing while they're under water and under pressure - the same reason air breathing water mammals do not get the bends.

However this doesn't address nitrogen that may already be present from earlier scuba dives.

Marc

 

[CBulla]

Dr D is on vacation for a week.. I saw that thread yesterday or day before I believe.

 

[H2Andy]

However this doesn't address nitrogen that may already be present from earlier scuba dives.

yes, this is exactly the issue. you dive, nitrogen is absorved
into your body under pressure, you come up, now the
nitrogen expands and starts to off-gas really nice...

ok... so now you go go down one half atmosphere (15 feet) and come back up quick, and and what happens? you just pushed the nitrogren into bubbles again and re-released them very quickly, again, which can lead to bubbles in the venous side compressing enough to get past the lungs and then re-expanding on the arterial side. if they lodge on the spine and brain blood supply, that's gonna hurt.

i have done this exact thing quite a few times, and never
got hit that i could tell. but the danger is there.