Free diving mixed with SCUBA?

[Jumpinghorse]

I received my Dive Master certification from an instructor who is also teaches free diving. When doing my DM training, he would insist that I practice my free diving during my surface intervals. I would argue with him that I felt it was not the safest thing to do because of the increase risk of DCS. He would always tell me and others that there was NO risk involved with free diving before or after SCUBA diving. Was I wrong or was I taking a great risk by practicing my free dives in between my SCUBA dives?
Thanks

 

[Gilldiver]

What you are doing is just about the same thing as a bounce dive to free a hook or bring up something off the bottom.

A free dive to any depth can cause problems if you have bubbles on the venous side. These bubbles should be collected and filtered out at the lungs. But, if you dive down to a depth where the bubbles have been compressed to a size where they can move back into the arterial side you can have problems with bubble traveling into the brain etc. This can be very similar to a PFO allowing for shunting of bubbles from on side to another in the heart. A central nervous system hit is not a thing to invite.

The danger area should be when you may be near the NDL or have been into DECO. If you are in either of these categories, then keep from free diving for 60 to 90 minutes. Diving on SCUBA within this time is not as much of a worry as you should be doing a slow and controlled accent with a safety stop. A free dive accent can easily be in the order of 120 feet/minute, as such you have no time for these bubbles to be recollected at the lungs and they can get trapped elsewhere and grow.

 

[Damselfish]

Free diving during surface intervals is generally considered to be a bad idea. I'd expect an instructor of all people to discourage it, not insist on it.

 

[SteveAD]

Even discounting the various "BAD THINGS" that might happen as a direct result of free diving during a surface interval, free diving absolutely WILL slow down your offgassing during the SI. As others have said, it is not a good idea.

 

[freediver]

Highly unfortunate that your instructor would encourage you to practice this. I also teach scuba and freediving and my rule of thumb is either scuba for the day or freedive for the day. Good to see you argue your point with the instructor. Continue to be wise and inform any students you may DM for.

 

[knotical]

These articles might help your instructor understand:

Breathhold Diving:Taravana

Can Freediving Cause DCS?

 

[Jumpinghorse]

Thank you all so much and thank you for the articles. I did read, ask other pros and did my my own research on the topic, and no matter how armed I was with information, the instructor always seemed to have an argument. It's never a good feeling to unbalance the role of the student-teacher relationship but it's not wrong to question that said instructor when something like this happens. I will be sure to always listen to students and provide the proper information to students when I am in the position to do so. Thank you again.

 

[bleeb]

Slightly OT, but can any instructors out there say whether free diving during surface intervals is a standards violation for any particular certifying agencies? Or particularly compelling them?

 

[Soggy_Diver]

It seems to me that once you have some nitrogen loading from scuba, even one rapid ascent is to be avoided. A single freedive is almost like having a rapid ascent at the end of a dive--another post already mentioned 120 ft/minute, which sounds accurate. Worse than that, freediving is like having a whole series of rapid ascents, one after another--maybe up to 20 freedives in an hour, if each is brief. Who wants to roll the dice on 20 rapid ascents in a row?

 

[DandyDon]

This was a Florida Keys Inst...?!