You apparently missed my explanation in which I placed the dive in a class of dives that are in a category of dives some people call "all usable." It does not matter whether it was a drift dive or any other such dive in which the diver does not have to get to a specific point to ascend. Here is where I wrote that:For purely recreational diving I don't bother to work out my bottom time before my first dive of the day. I jump in and follow my computer/gas limits. If either has a problem I just ascend.
This is a quote of the original post. There is no mention of drift diving.
It explains the difference between three major types of dive plans: rule of thirds, rule of halves, and all usable. A drift dive is just one example of an all usable dive--any dive where the diver is free to ascend to the surface at any point upon reaching an agreed upon PSI, time, or other turning point (like NDL). It could be a drift dive. It could be visiting a small wreck. It could be a lot of things common dives in diving. They are the simplest dives possible, and they have been covered in OW classes for years.
Here they are:What questions are you referring to?
So you consider going one direction until a specific PSI and then turning around a plan, but you do not consider going in one direction (like on a drift dive) until a certain PSI and then ascending to be a plan? Can you explain the difference?
Alos, what do you think was in the planning but not included in the post?
It is unusual for there to be more than a few minutes difference.No. Basically, what you mentioned in a previous post. The buddy team plans the dive to see if both computers agree with what the plan is. So no diver needs to cut the first dive short or jeopardize a latter dive. I am sure you have dove off of a commercial boat that needs to keep a schedule. You have some leeway over when to splash but if you wait to long the DM may not let you dive because they do not want to wait for you.
I do not understand your attitude on this. A dive computer is arguably the most complicated piece of equipment that a diver takes with them. In my 25+ years of diving I have seen them break, flood, and give off erroneous readings. Another problem is user error. I have seen people dive with the computer set to the wrong mix. I had a person once try to convince me that their Ai computer actually analyzes the mix in the cylinder and computes the NDL based on that. Is it really that difficult for the buddies to get together and plan the dives beforehand and say ok dive 1 is 30 minutes at 65 ft , we wait 60 and do a second dive for 30 minutes at 45 ft? Also shouldn't the buddies plan not to reach the NDL limits? The was a thread recently where a diver accidentally passed the NDL and decided it would be wise to ascend slowly. When doing so the computer started giving him ridiculously long safety stop info.[/QUOTE]Different dives have different planning needs. I will now describe two dives I have done within the last month to illustrate.
Dive #1--Chatfield Reservoir, Colorado. The maximum depth of the water was 21 feet. I was diving with someone to help them get used to his new equipment. We dived until we accomplished our goals. We knew we would never get near either NDLs or running low on air, so the instruments we carried were superfluous. We did not do anything resembling dive planning.
Dive #2--Rock Lake, New Mexico. We descended on a line to the bottom at 275 feet, where I tied off a large spool to the descent line. As planned, my buddy led us north using his compass, while I let out line so we could find our way back. I turned the dive just before my spool ran out of line because it was time to return to the ascent line so that we could ascend at our pre-planned time. I removed the spool line at precisely our planned ascent time, and we started up. At 190 feet, we stopped as planned to switch from the gas in our doubles (trimix with a lot of helium) to our deep deco gas (a mix of 21% O2 and 35% He). At 70 feet we switched to a mix of 50% O2. At 20 feet we switched to 100% O2. We each carried two computers, all with the same algorithm. We had carefully pre-planned the dive using our SAC rates to make sure we had plenty of each of the 4 different gases we used on the dive to cover not only the expected needs but any problems that might arise. We knew what kinds of of decompression stops we would probably be taking as we ascended, but we actually followed our computers for those stops. My computers and my buddy's computers disagreed by roughly two minutes by the time we were done, and we followed the most conservative one so that we would stay together on ascent.
Dive #2--Rock Lake, New Mexico. We descended on a line to the bottom at 275 feet, where I tied off a large spool to the descent line. As planned, my buddy led us north using his compass, while I let out line so we could find our way back. I turned the dive just before my spool ran out of line because it was time to return to the ascent line so that we could ascend at our pre-planned time. I removed the spool line at precisely our planned ascent time, and we started up. At 190 feet, we stopped as planned to switch from the gas in our doubles (trimix with a lot of helium) to our deep deco gas (a mix of 21% O2 and 35% He). At 70 feet we switched to a mix of 50% O2. At 20 feet we switched to 100% O2. We each carried two computers, all with the same algorithm. We had carefully pre-planned the dive using our SAC rates to make sure we had plenty of each of the 4 different gases we used on the dive to cover not only the expected needs but any problems that might arise. We knew what kinds of of decompression stops we would probably be taking as we ascended, but we actually followed our computers for those stops. My computers and my buddy's computers disagreed by roughly two minutes by the time we were done, and we followed the most conservative one so that we would stay together on ascent.
Most dives fall in between those two extremes. Before each dive, you have to decide what level of planning is necessary to remain safe, depending upon the logistics of the dive and the skill and experience of the divers doing it. What is essential for one dive may not even be necessary on another.