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Big Blue Diving - Koh Tao - Thailand - January 13th 2014



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Air pig-ery
air-pigAfter finishing teaching an SSI advanced course yesterday morning, I got to thinking about air consumption, as, you know, I need to get out a lot more. In the last blog post I wrote about the deep dive of the advanced course, and about how inert gas narcosis can impair judgement, and how it's important to know what to do to eliminate its effects. Monitoring your air consumption is also important on a deep dive, and you need to be checking it regularly. As you descend on a dive, you are being subjected to greater ambient pressure due to the increasing weight of water above you exerting additional force on your body's air spaces (plus the weight of the air in the atmosphere). If you can think back to Boyle's law from your school chemistry lessons, you'll know that the pressure and volume of a gas are inversely proportional. So, if you imagine a 1 litre balloon at the surface, then take that balloon down to 10 metres depth, the air inside will be crushed by the pressure of the water, so the pressure will be greater and the volume smaller (half the volume at 10m). The scuba cylinder containing your air is a rigid container, so the pressure and volume stay the same as you descend. But when the air comes out of your regulator into your lungs, your lungs are at the same ambient pressure as the water, so the air is compressed to that ambient pressure. But you still need to fill the same lung volume, so this means that you are basically breathing more atoms of air per breath. Thus, the deeper you go, the quicker you will go through your air. For a standard 11 litre cylinder, if you dive to 30 metres your dive time will be shorter than staying at 12 metres.
Bear in mind we need to ascend slowly from any dive, but especially from a deep dive, and it will take a few minutes to get from 30 metres to 5 metres for the safety stop. So keeping a good eye on your air is very very important. It's no good telling your buddy that you have 70 bar of air at 30 metres.. you WILL be sharing air before getting to the surface. 120 or 130 bar is a good rule of thumb to begin your ascent from 30 metres. Then you'll have plenty of air as you shallow up. Luckily, you're not a nutter attempting an open circuit world record deep dive. The official record is 318 metres, completed by South African Nuno Gomes in 2005. It took him 15 minutes to get down and 12 hours to get back up! At 250 metres, a standard 11 litre cylinder will give you approximately 11 breathes from full to empty!
Each dive of the advanced course introduces you to a different element of diving, and it's a perfect next step from the open water course. We run them every day, so give yourself 5 days when you come to Big Blue so you can continue your new addiction!

January kicked off as planned with Koh Tao being crazily busy. This means lots of people renting motorbikes to take in other parts of the Island, such as Tanote bay and Shark bay. Unfortunately it also means roads full of people who have no idea how to ride a motorbike, which inevitably ends in numerous crashes. Koh Tao tattoos are everywhere, with people wandering around with bandages all over their legs and arms from having wiped out on a bike. You can easily prevent this from being you. If you've never ridden a motorbike before, why would you think it would be a good idea to learn in a foreign country, where the rules of the road will be different from your own? If you can already ride a motorbike, just consider getting a taxi to wherever you want to go. They're not that expensive and you can go anywhere on the Island in one, or get a longtail taxiboat if you wish to go to one of the bays on the East or South coast. If you still insist on renting a bike, make sure you also rent a helmet, drive like a grandma and DO NOT drive when drinking. Also be aware of sand patches on the road, especially on bends. If you do crash, and hopefully don't injure yourself, you will have a hefty repair bill. The rental places will sting you, and they have your passport remember. If you do get into an argument over payment, you should call the police, as they are not allowed to keep your passport- it belongs to the Government where you come from.

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