Oh dear me, more flak. Some of you read far too much into things. Firstly I never said that diving sea caves without qualifications is safe - it is not. It is however the case that in the instance of that particular cave I was prepared to accept the level of risk that some consider unacceptable.
Regarding decompression diving I also know that you should be trained and build up to it gradually, not just leap off the boat with two tanks and hope for the best. [Edited by Moderator]
To get back to diving. There will be times when I want to go a bit deeper or stay down a bit longer than I can on a single tank. Several members of my club have chosen to do this by using CCR. However my interest in diving is such that I do not want to spend that amount on training or diving equipment. A basic decompression / technical diving course is not that expensive but the equipment is not available at many of the locations I dive.
I have seen a technical diving instructor dive as I have described earlier in this thread, an air tank on his back and nitrox hung on his D rings. Not only does he dive like this he dives solo like this at times. I do not know the % nitrox he was using but it would be less than 40%. I only spoke to him briefly and he said his reason for doing it was convenient when trimix was not available. To me this did not seem unreasonable and I thought it may enable me to have worthwhile dives to the 40m + wrecks at Scapa flow for example. This instructor was the only time I have come across anyone doing it, but it aroused my interest and that is why I posted to see if tables were available so I could assess the dive / bottom time advantage before pursuing it further.
More generally if people only did what they had learned from others we would still be living in the stone age or possibly not that advanced.
Regarding decompression diving I also know that you should be trained and build up to it gradually, not just leap off the boat with two tanks and hope for the best. [Edited by Moderator]
To get back to diving. There will be times when I want to go a bit deeper or stay down a bit longer than I can on a single tank. Several members of my club have chosen to do this by using CCR. However my interest in diving is such that I do not want to spend that amount on training or diving equipment. A basic decompression / technical diving course is not that expensive but the equipment is not available at many of the locations I dive.
I have seen a technical diving instructor dive as I have described earlier in this thread, an air tank on his back and nitrox hung on his D rings. Not only does he dive like this he dives solo like this at times. I do not know the % nitrox he was using but it would be less than 40%. I only spoke to him briefly and he said his reason for doing it was convenient when trimix was not available. To me this did not seem unreasonable and I thought it may enable me to have worthwhile dives to the 40m + wrecks at Scapa flow for example. This instructor was the only time I have come across anyone doing it, but it aroused my interest and that is why I posted to see if tables were available so I could assess the dive / bottom time advantage before pursuing it further.
More generally if people only did what they had learned from others we would still be living in the stone age or possibly not that advanced.