Recreational Scuba Deco Diving
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tmassey
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@boulderjohn brings up an important point in his post, above, #57. All "deco" dives are not created equal. Consider a 1st clean dive to 80 ft on air. This table could be expanded to include Suunto RGBM, Mares RGBM, Cressi RGBM...
Say we are instabuddies on a boat. We agree to do a no deco dive with a signal when NDL is 2 min, to start the ascent. You are diving Buhl 35/75 and I am diving DSAT. You "forget" to monitor your NDL and when I signal to start the ascent, you have a "surprised" look on your face and show me your computer in deco as we ascend. I do 2 min at 20 ft and then 5 min at 10 feet with you before we surface. It was such a short dive, we both have over 1000 psi remaining.
On this dive, my buddy accumulates 7 min of stop time while I never exceed my NDL. Was my buddy in much danger if he would not have recognized he was in deco, probably not, we would have done at least a 3 min safety anyway.
I made up this story, but, this scenario has played out a few times during my years of diving. I generally dive solo, when I do have a buddy who is not known to me, I take steps to make sure that this doesn't happen. How many of you have had divers come up to you, as I have, and ask if you know what is wrong with their computer and the answer is it appears they missed deco and are in violation gauge mode?
Say we are instabuddies on a boat. We agree to do a no deco dive with a signal when NDL is 2 min, to start the ascent. You are diving Buhl 35/75 and I am diving DSAT. You "forget" to monitor your NDL and when I signal to start the ascent, you have a "surprised" look on your face and show me your computer in deco as we ascend. I do 2 min at 20 ft and then 5 min at 10 feet with you before we surface. It was such a short dive, we both have over 1000 psi remaining.
On this dive, my buddy accumulates 7 min of stop time while I never exceed my NDL. Was my buddy in much danger if he would not have recognized he was in deco, probably not, we would have done at least a 3 min safety anyway.
I made up this story, but, this scenario has played out a few times during my years of diving. I generally dive solo, when I do have a buddy who is not known to me, I take steps to make sure that this doesn't happen. How many of you have had divers come up to you, as I have, and ask if you know what is wrong with their computer and the answer is it appears they missed deco and are in violation gauge mode?
In my case, I had an unlimited season pass for the charter boat and cost was a non-issue. People without passes were paying $180, or roughly $12/min BT.
It makes much more sense in terms of cost, safety, AND fun to dive wrecks in the gray area between rec/tech as planned technical dives.
I think that there could be a market for instruction on "ultra-light" deco/backgas deco as a stepping stone to accelerated deco courses.
1. Seldom (once)
2. Shore (cenote)
3. Fresh
4. Buddy (DM + 2 others + me)
5. Single - DM had a large Pony
6. Planned - (Drop to 40m quickly then slow ascent circling the Cenote)
7. Sightseeing
Interesting this was a guided Cenote dive near Playa del Carmen in Mexico and I learned of the plan to go past the No Deco Limits in the predive briefing about 15 minutes before we splashed. I was Ok with it but someone wan't and the were not particularly outspoken they may not have felt comfortable raising their concerns. Just looked no and the most my computer was asking for was a 2 minute stop at 3m which disappeared by the time we had ascended to 18
2. Shore (cenote)
3. Fresh
4. Buddy (DM + 2 others + me)
5. Single - DM had a large Pony
6. Planned - (Drop to 40m quickly then slow ascent circling the Cenote)
7. Sightseeing
Interesting this was a guided Cenote dive near Playa del Carmen in Mexico and I learned of the plan to go past the No Deco Limits in the predive briefing about 15 minutes before we splashed. I was Ok with it but someone wan't and the were not particularly outspoken they may not have felt comfortable raising their concerns. Just looked no and the most my computer was asking for was a 2 minute stop at 3m which disappeared by the time we had ascended to 18
J-Vo
Contributor
Blackcrusader
Contributor
Well part of the buddy check is knowing what setting your buddy has yes? I know that when I do repeat dives with the same DM who uses a Suunto he will have much less time to NDL than my Perdix due to settings over repeat dives. So a good buddy check would note the GF setup on each dive computer. Very easy to miss though as people often would not ask. I often have to advise dive buddies to dive to their own computer as I have 45/95 GF on my perdix. I had one buddy who ended up with a very long safety stop after I did a 25m dive for 28 minutes and her Suunto had exceeded NDL whereas I had 5 mins to NDL. Her Suunto on the default conservative setting.
Anyway it is a divers responsibility to monitor their own NDL and air so if they just follow along and never check then these things can happen. I dive with my Perdix in OC TEC mode not basic air or nitrox mode as I want to have the extra information. .
tarponchik
Contributor
1. Occasionally
2. Shore
3. Marine
4. Solo
5. Single
6. Plan to get no more than 5-10 min deco time
7. I did all my deco dives in Hawaii to explore the deep marine habitats
2. Shore
3. Marine
4. Solo
5. Single
6. Plan to get no more than 5-10 min deco time
7. I did all my deco dives in Hawaii to explore the deep marine habitats
Blackcrusader
Contributor
A new RSDD diver on his deep training dive with a DM. I assume the DM is his instructor 
He only had to to a few deco stops on the ascent ......
First dive at 40 meters - Newbies recreational
He only had to to a few deco stops on the ascent ......
First dive at 40 meters - Newbies recreational
J-Vo
Contributor
I don't change my PDC out of "tech" conservatism for NDL dives, so 3min deco stop is the same as 3min safety stop for me. Does that count as back gas deco? If my PDC does not call for deco, I don't need a safety stop.
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