Dive Computer or Tables - which is safer for a newer diver?

[PfcAJ]

I just watched a review of your BT. I agree it is a very cool device, and for most of my dives it would be really cool to have. the down side is that much of the info that it gives does not replace the moost critical information that a dive computer provides. If you end up to deep being somewhat narced on what was orginally intended to be a NDL dive and find that you went an exttra 20ft, all the cool displays in the world are useless when what you really want are decmpression stops and times. you could use the old square profile and the your Dive tables to figure it out. That is a safe but crude calculation and will not be the most gas efficient measure. An accidental Deco dive implies that gas available is going to be a critical issue. I would love to dive with your bottom timer, but for $500 it is not giving me the utility that I carry the computer for. Even on my el-cheapo genesis computer, I get a graphical representation of how close I am to the NDL. For Safety, that trumps just about every log function imaginable.

I like the dive simulation feature it would be awesome for planning a complex dive profile, but again, it isn't helping with the NDL that I would value most.

But still it is a sweat piece of gear, and if you mail me one I would use it every time....

What's unsafe is getting in the water without a plan.

It takes almost no effort at all to know the NDL times for various depths with air or 32% nitrox, and exceeding your planned depth to a point where you're "narced" and don't notice it is a poor argument. Even memorizing the procedures for violating your NDL times are extremely simple. Required deco (the type you get because you genuinely were delayed at depth, not because you can't plan a dive and follow the plan) and the short/shallow stop times that it requires shouldn't make your gas supply critically low if you have a sound gas plan (minimum gas). Of course, if you (and your buddy) ignore your gas, time, and depth parameters, all bets are off, and a magic box isn't going to save the day.

You've got to pay attention.

 

[CT-Rich]

What's unsafe is getting in the water without a plan.

It takes almost no effort at all to know the NDL times for various depths with air or 32% nitrox, and exceeding your planned depth to a point where you're "narced" and don't notice it is a poor argument. Even memorizing the procedures for violating your NDL times are extremely simple. Required deco (the type you get because you genuinely were delayed at depth, not because you can't plan a dive and follow the plan) and the short/shallow stop times that it requires shouldn't make your gas supply critically low if you have a sound gas plan (minimum gas). Of course, if you (and your buddy) ignore your gas, time, and depth parameters, all bets are off, and a magic box isn't going to save the day.

You've got to pay attention.

I agree with you 100%. I was stating a hypothetical ( I have been reading a book about diving the Andrea Doria, someone always dies bent in those books) Sorry if I was getting melodramatic. I am yet to find myself in that situation, and don't plan on it either. I have a simple computer that keeps track of bottom time and depth and an eye on the NDL. I know what the limits are respect them. But, there are plenty of opportunities to do stupid things and a computer that cost $150 lets me monitor all the stuff I want and will tell me if I am F***ing up is a good thing. I have multiple tanks and the nice thing about a computer is that it will monitor multiple dives, so that I can get the most out of my diving. Should a diver dive without a computer? consdering that simple and reliable one is available and will help you monitor your time, depth and water temperature, I would say it is a perfectly reasonable expense when compared with the overall cost of diving gear. A nice dive watch that is suitable for wearing around town and proper depth gauge combined costt as much as a computer, why not just buy the computer? When planning a dive I use the standard NAUI table I bought when I was 18. My computer is a single instrument that I am familiar with and does a lot, why leave it in the bag?

Diving is a lot of fun, and the technology available today is more reliable than was available in 1980. Why not invest in gear that makes it that much easier and safer? I hated diving with an oral inflation horse collar BCD. I have no expectation that a new diver should learn how to use them. A solid understanding of the gas laws is critical, including how use the tables. But I don't see any reason to say a computer is a waste of money. A new dive rig can cost thousands, why cut that particular corner? I would rather have a new diver get in the habit of monitoring their dives from day one, even if it is twenty minutes at 20 fsw.

that is teaching them to pay attention.

 

[BluewaterSail]

I agree with you 100%. I was stating a hypothetical ( I have been reading a book about diving the Andrea Doria, someone always dies bent in those books) Sorry if I was getting melodramatic. I am yet to find myself in that situation, and don't plan on it either. I have a simple computer that keeps track of bottom time and depth and an eye on the NDL. I know what the limits are respect them. But, there are plenty of opportunities to do stupid things and a computer that cost $150 lets me monitor all the stuff I want and will tell me if I am F***ing up is a good thing. I have multiple tanks and the nice thing about a computer is that it will monitor multiple dives, so that I can get the most out of my diving. Should a diver dive without a computer? consdering that simple and reliable one is available and will help you monitor your time, depth and water temperature, I would say it is a perfectly reasonable expense when compared with the overall cost of diving gear. A nice dive watch that is suitable for wearing around town and proper depth gauge combined costt as much as a computer, why not just buy the computer? When planning a dive I use the standard NAUI table I bought when I was 18. My computer is a single instrument that I am familiar with and does a lot, why leave it in the bag?

Diving is a lot of fun, and the technology available today is more reliable than was available in 1980. Why not invest in gear that makes it that much easier and safer? I hated diving with an oral inflation horse collar BCD. I have no expectation that a new diver should learn how to use them. A solid understanding of the gas laws is critical, including how use the tables. But I don't see any reason to say a computer is a waste of money. A new dive rig can cost thousands, why cut that particular corner? I would rather have a new diver get in the habit of monitoring their dives from day one, even if it is twenty minutes at 20 fsw.

that is teaching them to pay attention.

What percentage of divers do you think do "trust me" dives with their computer? Just swimming around until their air integrated computer tells them its time to come up?

Thats the danger with computers. Laziness. Its just too easy not plan, and not to stay aware of depth, time, and gas.

Also, I have seen people do what I think you described; using a computer to stay on the edge of the NDL to get the "most" from their dives. I wouldn't do that or recommend that. I prefer to dive more conservatively. I don't want to be on the bottom line of the tables, where a small unforseen event forces you over the edge into deco. I hope that you weren't recommending to new divers to do that.

I wouldn't call a computer a waste of money. But I believe that if it is used to replace awareness and/or planning, that it is dangerous. If it is used to confirm what you already know, providing a reference for deviations, then it could be a valuable tool.

 

[Them]

Laziness is not a danger of computers.

Laziness isn't even the danger. The word is carelessness. As in, "I don't care enough to put any effort into this."

Carelessness exists regardless of computers. If you think the people who stop planning dives only do so because they have computers you are wrong. I haven't been diving long but I have already seen people say, "I've dived this before, I don't need to plan," and they didn't have computers.

 

[CT-Rich]

What percentage of divers do you think do "trust me" dives with their computer? Just swimming around until their air integrated computer tells them its time to come up?

Thats the danger with computers. Laziness. Its just too easy not plan, and not to stay aware of depth, time, and gas.

Also, I have seen people do what I think you described; using a computer to stay on the edge of the NDL to get the "most" from their dives. I wouldn't do that or recommend that. I prefer to dive more conservatively. I don't want to be on the bottom line of the tables, where a small unforseen event forces you over the edge into deco. I hope that you weren't recommending to new divers to do that.

I wouldn't call a computer a waste of money. But I believe that if it is used to replace awareness and/or planning, that it is dangerous. If it is used to confirm what you already know, providing a reference for deviations, then it could be a valuable tool.

I haven't been to Bonaire, but when I get the money to spend on a really great dive trip, I would hope that I get as much bottom time as I can for the money, time and expense. A dive computer's algorythm gives a much more accurate reflection of of what was actually occurring on a given dive than the dive tables can. Most dive computers for sport diving are plenty conservative for a large safety margin. I wouldn't recommend diving right up to the NDL, otherwise the scenario I gave in my earlier post becomes much more likely. Most newly certified divers are not going on dives where a computer will be of real value. Two or three single tank dives in less than 60fsw are not likely throw them over the line, especially on a vacation charter where a dive maaster is going to be supervising.

Should they be looking at the tables? yes. A basic computer can't be used to plan a dive or multiple dives. I think the use a computer on a regular basis gets you into a lot of good diving habits, like looking at your gauges even though you could get by with out it. Importantly, a computer gives you functionality for several gauges in one. Less confusing junk for a Noob to get confused by. And in a worst case scenario, it will help them avoid a serious lapse in judgement. Some one else may have heard of an episode, but I haven't. How many documented cases have there been of a diver getting into trouble by relying on the calculations made by a properly functioning, properly used dive computer? My guess is that the number is fairly low. I am much more likely to read off the wrong column on a dive table than a computer is. The computer will never forget to set the watch or check the depth at regular intervals.

Of course there are limits, there is no known cure for stupid. A OW student or AOW diver with 12 dives are often not completely familiar with there gear, the tables or good diving practices. the likelyhood is that they will burn through their air pretty quickly, I would worry more about hyperventilation, anxiety attacks, panic and poorly maintained rental gear before I worry that they are going to get any where near the NDL. I would like them to start out learning to monitor there gauges and surroundings in a way that they become conscientious divers.

For clarity, my analogy about the horse collar was not about whether they should learn the tables or not (they should), but I think when some technological advancement comes along that can make diving significantly safer and less stressful (like power inflators and Jacket BCDs), it should be embraced. Dive computers are huge improvement in diving, under standing the tables is important for planning and also for understanding in a overly simplifed way how the computer is thinking about your dive profile.

 

[weitodive]

My answer is simple. The one they are willing to actually take the time to understand and use.

 

[Pullmyfinger]

I just watched a review of your BT. I agree it is a very cool device, and for most of my dives it would be really cool to have. the down side is that much of the info that it gives does not replace the moost critical information that a dive computer provides. If you end up to deep being somewhat narced on what was orginally intended to be a NDL dive and find that you went an exttra 20ft, all the cool displays in the world are useless when what you really want are decmpression stops and times. you could use the old square profile and the your Dive tables to figure it out. That is a safe but crude calculation and will not be the most gas efficient measure. An accidental Deco dive implies that gas available is going to be a critical issue. I would love to dive with your bottom timer, but for $500 it is not giving me the utility that I carry the computer for. Even on my el-cheapo genesis computer, I get a graphical representation of how close I am to the NDL. For Safety, that trumps just about every log function imaginable.

I like the dive simulation feature it would be awesome for planning a complex dive profile, but again, it isn't helping with the NDL that I would value most.

But still it is a sweat piece of gear, and if you mail me one I would use it every time....

I believe that diving with a bottom timer and a plan derived from a review of the table, might contribute to not doing those things.
I've heard these points made before, and I think some divers use their computer as a crutch against not planning and then following that plan.

**I'll add that my definition of "planning" a dive is likely different that others. Riding the NDL display on a computer is NOT a plan. Squeezing every last bit of gas from your tank, just because the computer tells you that you have more NDL time, is also NOT my definition of a plan.
I have know quite a few divers that did exactly that BECAUSE they had a computer.***

Just something to consider.

I guess it has more with how each is utilized by the diver rather than a debate over with is better/necessary.

Most of us forum users are experienced enough to have decided what works best for each of us....so there are many good approaches.

In terms of me giving an answer to a new diver as to whether or not they need a computer?
I'd suggest, "No. They don't".

Spend their money on all of the other necessary equipment first. They may decide that after diving awhile, they may not ever feel the need for a computer at all.

If they reach the conclusion that they want to use a computer for their diving....well, there are plenty out there to choose from.



-Mitch

---------- Post Merged at 07:44 PM ---------- Previous Post was at 07:27 PM ----------

I haven't been to Bonaire, but when I get the money to spend on a really great dive trip, I would hope that I get as much bottom time as I can for the money, time and expense. A dive computer's algorythm gives a much more accurate reflection of of what was actually occurring on a given dive than the dive tables can. Most dive computers for sport diving are plenty conservative for a large safety margin. I wouldn't recommend diving right up to the NDL, otherwise the scenario I gave in my earlier post becomes much more likely. Most newly certified divers are not going on dives where a computer will be of real value. Two or three single tank dives in less than 60fsw are not likely throw them over the line, especially on a vacation charter where a dive maaster is going to be supervising.

Should they be looking at the tables? yes. A basic computer can't be used to plan a dive or multiple dives. I think the use a computer on a regular basis gets you into a lot of good diving habits, like looking at your gauges even though you could get by with out it. Importantly, a computer gives you functionality for several gauges in one. Less confusing junk for a Noob to get confused by. And in a worst case scenario, it will help them avoid a serious lapse in judgement. Some one else may have heard of an episode, but I haven't. How many documented cases have there been of a diver getting into trouble by relying on the calculations made by a properly functioning, properly used dive computer? My guess is that the number is fairly low. I am much more likely to read off the wrong column on a dive table than a computer is. The computer will never forget to set the watch or check the depth at regular intervals.

Of course there are limits, there is no known cure for stupid. A OW student or AOW diver with 12 dives are often not completely familiar with there gear, the tables or good diving practices. the likelyhood is that they will burn through their air pretty quickly, I would worry more about hyperventilation, anxiety attacks, panic and poorly maintained rental gear before I worry that they are going to get any where near the NDL. I would like them to start out learning to monitor there gauges and surroundings in a way that they become conscientious divers.

For clarity, my analogy about the horse collar was not about whether they should learn the tables or not (they should), but I think when some technological advancement comes along that can make diving significantly safer and less stressful (like power inflators and Jacket BCDs), it should be embraced. Dive computers are huge improvement in diving, under standing the tables is important for planning and also for understanding in a overly simplifed way how the computer is thinking about your dive profile.

Sorry if it seems like I'm singleing you out Rich. Your posts brought up a few good points.

Even if I'm on a dive trip, I still go by the same gas planning rules as I do for local diving. I do understand the temptation to get maximum bottom time because of the expense involved with dive trips.
But the same gas planning rules apply no matter where we all dive.

I know there would be a lot of subjective answers, but how many bottom timer divers vs. computer divers know their gas consumption rate and apply that information toward their dive plan?

When people point out the "advantages" of doive computer use, that part of the dive plan sort of get left out of the arguement.
When gas supply duration get introduced into the comparison, the advantages that are often mentioned for a computer can be reduced.

For many dives, gas supply duration is more of a driving factor in the plan than NDL is......even more so when you factor reserve gas.
The computer can't really "give" you more time, if you don't have the gas supply and reserve gas to take advantage of that time.

v/r,
Mitch

 

[NAM001]

Airplanes have a black box, divers have the computer , dead or bent divers do not talk. But thier computers do. What better group of divers to use one than a new diver that can go back to review thier dive. having one and being dependant on one is 2 different things. there is a lot to learn watching the computer when it says that you have 5 min to ndl and when you go shallower you now have 15 to ndl. it provides a great real life example of cause and effect training when it comes to depth and time as it effects ndl. and what happens when you go into deco and then you go shallow and the deco requirement go's away. You cant buy training of the type that the computer monitoring can provide. Some may call it riding the ndl line. I call it getting the most safe time out of my dive. It reinforces doing the deep stuff first and the shallower stuff later. what better understanding of time to ndl can you get than from a dynamic readout. no set of tables can do that. Many parents would not think twice about putting a monitor on thier kids car to keep track of what they are doing. Whats the difference? One thing for sure tha computer dive profile will tell you just how well you stuck to your planned dive.

 

[CT-Rich]

I believe that diving with a bottom timer and a plan derived from a review of the table, might contribute to not doing those things.
I've heard these points made before, and I think some divers use their computer as a crutch against not planning and then following that plan.

**I'll add that my definition of "planning" a dive is likely different that others. Riding the NDL display on a computer is NOT a plan. Squeezing every last bit of gas from your tank, just because the computer tells you that you have more NDL time, is also NOT my definition of a plan.
I have know quite a few divers that did exactly that BECAUSE they had a computer.***

Just something to consider.

I guess it has more with how each is utilized by the diver rather than a debate over with is better/necessary.

Most of us forum users are experienced enough to have decided what works best for each of us....so there are many good approaches.

In terms of me giving an answer to a new diver as to whether or not they need a computer?
I'd suggest, "No. They don't".

Spend their money on all of the other necessary equipment first. They may decide that after diving awhile, they may not ever feel the need for a computer at all.

If they reach the conclusion that they want to use a computer for their diving....well, there are plenty out there to choose from.



-Mitch

---------- Post Merged at 07:44 PM ---------- Previous Post was at 07:27 PM ----------



Sorry if it seems like I'm singleing you out Rich. Your posts brought up a few good points.

Even if I'm on a dive trip, I still go by the same gas planning rules as I do for local diving. I do understand the temptation to get maximum bottom time because of the expense involved with dive trips.
But the same gas planning rules apply no matter where we all dive.

I know there would be a lot of subjective answers, but how many bottom timer divers vs. computer divers know their gas consumption rate and apply that information toward their dive plan?

When people point out the "advantages" of doive computer use, that part of the dive plan sort of get left out of the arguement.
When gas supply duration get introduced into the comparison, the advantages that are often mentioned for a computer can be reduced.

For many dives, gas supply duration is more of a driving factor in the plan than NDL is......even more so when you factor reserve gas.
The computer can't really "give" you more time, if you don't have the gas supply and reserve gas to take advantage of that time.

v/r,
Mitch

I don't think we are actually that far apart. I was certified in 1980 and the tables were what we had, and I didn't even have a decent bottom timer. The margin of error for planning a dive was very large because you had to have a square profile and you were always rounding to the longer time/deepest depth. But the human error that was brought into the equation was also significant. A computer can help you monitor a dive and if you made a planning error it let you know when that error puts you at risk. Better data = better options. Plan the dive, dive the plan still applies. but a dive computer will make monitoring the dive easier and less prone to human error. New divers have a lot of situational awareness issues, I was skin diving with a my daughter last weekend and a diving student popped up right in front of me because he freaked out in 12 fsw. They have a lot to absorb and remember, but they don't stay that way forever. they need to develop good habits from early on. Monitoring depth and time are important. a simple computer can do that as well or better than the non computer options in a single device. The $500 bottom timer is awesome, but it is overkill. I have a friend with a wetsuit and drysuit and around 30 dives. he has a nice rig and is becoming more and more proficient at using the gear. The dive computer is a relatively small expense by comparison and has a high degree of utility.

I have not sat through a modern openwater course, so I can't say what the training is like. From what I heard it is not as rigorous as what I was given in 1980. I remember sitting at home practicing dive profiles until they were easy and reciting the NDL until they were instinctive (those are still the numbers I think of).

A plastic chart or a dive computer is no substitute for practice. A dive computer is not a substitute for a human brain. If a new diver is overly reliant on a computer, it is not the computers fault. It is the an issue of training and poor choice by the diver. Gas management is a more likely issue for a new diver than the NDL, and a computer won't help them with that, but again, a dive computer will provide accurate data about the dive profile that can be valuable in determining SAC. and that is alway of value in future planning.

When I started, I was still in high school and I did okay with a lot less. A computer is not critical, but I would buy it before I spent a lot of money on some other stuff. I still would consider it a piece of gear that needs to be understood and used wisely.

---------- Post Merged at 07:43 AM ---------- Previous Post was at 07:34 AM ----------

It reinforces doing the deep stuff first and the shallower stuff later.

I hope this isn't how divers are learning about deep to shallow

 

[PfcAJ]

The $500 dollar Xen is a trinket, imo (and I own one, and I like it a lot). My Uwatec Digital Depth Gauge cost me like 120 bucks, and it still accompanies me on dives.

Computers all too often become a crutch. And, fwiw, I do think that it is the computer's fault. If you computer didn't exist, people would be more inclined to possess proficiency with tables. I do not find them to have as much utility as having a functional knowledge of tables and proper (recreational) deco procedures.

Beeping alarms, flashing numbers, mystery modified algorithms (probably my biggest gripe with computers). Pointless and not needed.