Is free diving during surface interval a problem?

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gregpsych

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My son is in great shape. He can easily free dive to 35 or 40 feet with little of no effort. He likes to do some snorkling and free diving during the surface interval. While in Grand Cayman an instructor diving on the same boat with us said that was not a good idea because of the the release of nitrogene bubbles due to free diving. Does any one know if this is true or not? Is he taking a risk?

Greg
 
Greg, he's definitely taking a risk. Word is to always freedive before scuba not after, and never during a surface interval. The instructor on the boat was correct. Your son should check the website http://www.deeperblue.net Information on freediving, how to do it safely, the dangers of it and what techniques to avoid, are just a very few of the things he'll find there.
 
gregpsych:
My son is in great shape. Is he taking a risk?

Greg
Click to expand...

Yeh the better he is at freediving. the bigger the risk. Would you let him bounce down with a tank for a minute dive for maybe 10-15 times to a depth of 40 feet, and then shoot up at 100 ft per minute? Thats equivalent to what any decent freediver could do in 45 minutes, without even pushing himself.
 
snorkeling is no problem, but it is the rapid descent and ascents of freediving that can cause serious problems.

When a diver that is well within normally accepted ND limits does a rapid ascent, they can get what is called shock decompression.

You can relate this to the party trick of hitting a beer bottle on the top with the bottom of another, making it overflow. The beer was gassing off nicely, but the shock of hitting it with another bottle dislodges microbubbles, creates micronuclei, unleashes the deco genie, who knows, but it causes problems.

I believe that the body works in a similar way.

My only experience of shock decompression was a lady who was hanging from a safety stop bar when the boat swung and she was shot to the surface. She had deco symptoms, but only in one leg. Not the whole body.
 
Ditto what the others have said, why risk it freediving, just do some surface snorkeling and give your body time to offgas the Nitrogen he's already built up from diving.

C U underwater, :snorkel:
ScubaDivaDivemaster
 
http://gue.com/Projects/WKPP/Decompression/nobounce.html

the issue is not dissolved nitrogen but free-phase bubble showers following a dive. if you freedive then you can compress those bubbles, shunt them past the alveolar beds and then re-expand them on the arterial side. if those arterial bubbles go to the brain, they can lodge in capillaries causing a bad type 2 hit.
 
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