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Most recreational divers will never experience depths of 50m, but we recently had the opportunity to do just that without even getting our feet wet.
Dry diving should not be confused with scuba diving in a dry suit. There is a big difference. When you do a dry dive, you sit in a recompression chamber which artificially pressurises your environment.
The purpose of our dry dive was to experience the effects of Nitrogen Narcoses. Nitrogen Narcoses happens when scuba diving at depths greater than 30m. When you breathe air, which is predominantly made up of Nitrogen, under elevated pressure, it affects mental functions in the scuba diver. The effects are similar to alcohol intoxication. The narcosis itself is not dangerous, but just like excessive drinking makes people do stupid things, so impaired mental functions can cause a safe diver to do reckless things. It is essential therefore for those that do deep dives to be aware of what it feels like when they experience narcosis so that you can take steps to manage it.
On to the dry dive....
First off I must warn you that you should wear shorts and a t-shirt when you do a dry dive. I had the pleasure of doing it in jeans and a shirt and then ended up sweating a lot. The reason for this is that air under pressure heats up. So as the pressure increases in the chamber, you will experience an increase in heat and humidity.
They squeezed (not really) six of us in the recompression chamber and closed the hatch. You get issued with a bucket of water...no not for drinking, but as a safety mechanism. There is a slight risk of fire, so don't go in with lighter fluid on you.
There is an intercom that connects you to the operator on the outside of the chamber, so if you feel uncomfortable, feel free to let him know. They start the dry dive off by taking you down to 9m. If you can make it to 9m without experiencing equalisation problems you are good to go all the way. Oh yes I almost forgot...you get given some condoms to take with you.... no it is not what you are thinking! The idea is to blow them up and see the effects that the pressure has on the air in the condom at pressure. The group that went before us blew the condom up at about 9m...guess what happened when they came back up...you guessed it...it burst.
When the process starts, the compression takes place at quite a rapid rate so you have to equalise very often. Within a matter of minutes you go from 9m to 50m. At about 50m I noticed that some of my companions were acting a bit funny...there was a lot of giggling taking place. At that point I still felt fine and wondered what the big fuss was about. About a minute later I started feeling very relaxed... kind of the way you feel after you have had your second double brandy and coke. At that point we discovered that when you speak at a pressure equal to 50m your voice sounds like you have been breathing helium. That of course got everyone laughing their heads off.
After about 5 minutes at 50m they start decreasing the pressure slowly. As the temperature starts to drop the moisture in the air starts to condensate and a mist cloud forms in the chamber. This happened a few times as we hit different pressure depths.
The experience takes about 30 minutes and is well worth it. We had lots of laughs and I learnt allot. Not only did I learn what Nitrogen Narcosis feels like, but I had some fun with friends as well. Oh and I was sopping wet...so the dive was not that dry after all. PS... when you do a dry dive, you can’t dive or drink alcohol for at least 18 hours after the experience.