I witnessed something stupid & potentially very dangerous on a recent dive.

[Zeagle Eagle]

Originally Posted by Daz

So what happened to the moray? Was he OK?

The moray was fine, a little fishy, but Louisiana Hot sauce fixed that.


PS: I am a member of the PETA society.....that's People Eating of Tasty Animals.

[Rockhound76]

We used to snorkel with the manta rays on surface intervals at the Flower Gardens. Those rules have now been changed.

I have heard numerous anecdotes on diver's getting bent doing this, but I've yet to witness it and yet to read a definitive study on the causes (more complex than simple bounce diving. N2 is uptake it limited to a single breathe each "dive" and a varying partial pressure profile as O2 and CO2 are exchanged. Residual post-scuba N2 outgassing is suppressed by as single--usually--compression/decompression cycle with every bounce.)

I'm sure DAN has something on this...I'll research it. (Ahem...I was obviously a Darwin Candidate, as i would free dive on almost every trip to the Gardens back then.) I followed a very unscientific rule of "no more than 10' or 30 seconds". Now my rule is "don't do it." God, I miss those manta rays....

[RMur]

Originally Posted by Skinsfan1311

Last week we were diving in Grand Cayman.

The first dive of the day was a max depth of around 100'.

We headed over to the second dive site, which was a very short boat ride. Some of us were jumped off the boat, to cool off, float around, snorkel, (pee!), whatever, during our surface intervals.

Upon hearing that the top of the coral-head below was only about 40', this one guy tells his wife that he's going to dive in and see if he could touch it. He then proceeded to try to do so.

Bear in mind, that we were only about 15 minutes into our SI's!.

The DM was quite irate and told the guy that "I've seen people get bent pulling stunts like that! Do not ever do that again!"

Fortunately, the guy did not seem to suffer any injuries, but that sure was an eye-opener and a pretty valuable lesson.

I'm also kinda embarrassed to say that as I watched the guy pull that stunt the thought that it could be dangerous never even crossed my mind!

I've definitely filed that in my "lessons learned" category.

I've got to plead ignorant on this one.

Why would you expect this diver to get bent free-diving to a 40' depth?

It seems to me that:

1. He wold still have residual N2 in tissues after the first (100') dive.
2. He would introduce additional N2 into his tissues during the free-dive and 3. Increase his surface interval by some small amount.

But, it seems to me that bouncing down to 40' would not present a large risk of getting bent given the "bottom" time of probably less than a minute.

Surface intervals are not "fixed" anyway. If the guy chose to do the first dive at 100', take a 15' surface interval (while the boat moved) and do a subsequent 40' dive - he would simply have a shorter 40' dive - yes?

The problem must be in the introduction of the "bounce" back to the surface during the free dive?

[WaScubaDude]

Rmur,
You are on the right track. It is the quick ascent that is likely causing problems, not so much the quick decent when free diving during a surface interval.

[tndiverdude]

That would have been just desserts fire coral.
Some guys are just show offs, and a majority of them will one day become a rescue or at the very least a Darwin Diver award winner.

jimmy

[OTGav]

OK so I haven’t checked the books, but this is my (half) remembered version of why it’s bad to free dive after Scuba – this may only be theoretical, ask good old Uncle DAN for actual evidence.

Most/all divers have small bubble formation post dive that doesn’t cause issues – silent bubbles. These are mostly caught in the lung structure and gas exchange away efficiently there.

Blood comes from around the body to the lung, get some O2 and then is passed on to feed the heart, brain, and on to the rest of the body.

This is why PFO is a problem, the silent bubbles can occasionally pass across the heart (through the hole) bypassing the lungs trap and go straight on the brain and body. So a dive that causes no problems for other divers can be bad news for someone with PFO.

Post dive, if you have silent bubbles in your lung (you do) happily starting their gas exchange and then go free diving, you recompress the gas, shrinking/dissolving the bubbles. It can move past the lung’s bubble traps, through the heart, and on to important stuff like the groin, or brain – take your pick.

At the end of your breath you pop up to the surface and the gas drops out of solution again in it’s new home, this could be bad – it’s a self induced PFO in a way, it won’t get you every time, but it can get you.

I think that makes sense and is about how I remember things working. Experts can correct me if I'm way off base.

Thanks.

[bane51031]

What a moron, careless/reckless not only is it a NO NO why in the hell would he even think it was Kosher to try and touch the coral, someone should of kicked in the Jimmy.....

[doggie]

so how long after scuba you can start free diving?

[scubadiver888]

Originally Posted by doggie

so how long after scuba you can start free diving?

Hi doggie,

I doubt there are real numbers on this. If you think about multiple dives on scuba. If i did a dive to 100' then I wanted to do a second dive to 50' I would use my dive tables to calculate the surface interval required to do a no-stop dive. The tables assume I'll be breathing compressed air at depth. This will add more nitrogen to my system. So I have to calculate my maximum bottom time for the second dive as well.

With free diving after scuba, you could look at the free dive as a second dive. However, since you are not going to be breathing compressed air on the second dive, it would be like doing a bounce dive (1 second at the second depth). So there would be no need to calculate the bottom time for the second dive but you can still use your dive tables to calculate the surface interval.

This is all theoretical and with anything related to diving, it will reduce your chances of DCI but never eliminate it.

[rpowton]

Also with the free diving after a scuba dive even though you may add an interval and reduce your residual nitrogen unlike a second scuba dive where you will make a slow ascent with a stop at 15' on a free dive you will do a rapid descent and rapid ascent cycle potentially triggering the small bubbles to become larger bubbles with the potential for DCI.