Dive Computers vs. Dive Tables

by Sean Harrison:

Picture this – I’m riding to the dive site on my horse and buggy, and calculating my no decompression limits on my abacus. If you think that takes time, that’s nothing, it’s chiseling my dive plan into my stone tablet – now that’s a real hassle. But hey, on the bright side, I don’t need a weight belt when I carry my dive plan!

This is all in fun but gets to the point that human nature is to advance, to learn and to progress, and with this comes change. Perhaps the most significant change in our industry was the introduction of the dive computer. Why was it so important? Because before we had it – we, as recreational divers, used dive tables which had some significant limiting factors. Here are just a couple of examples: they were developed for “square profiles” (where the diver hits the deepest depth and stays there for the total time allotted) and, the information the tables were built upon was derived from young male divers. Dive tables are by no means obsolete; they still have their place in diving. For instance, they are critical in planning a technical dive where the diver’s entire time may be spent at maximum depth, and they are needed to explain the evolution of diving and their role in history.

Dive tables are just one example of an advancement that has improved safety and made diving more accessible to a wider range of people. Some other notable advances are K valves, jacket and backmount BC’s, and the octopus. Some other items gaining popularity include personal emergency position indicating radio beacon (EPIRB), diver VHF radios, and surface marker buoys (SMB).

Personal dive computers not only improved the safety of diving by tracking in real time what the diver was doing, they also made it easier for the diver to log their dives, first by providing a dive log and then by allowing dives to be downloaded to a computer. Further advancements with some computers allowed for multiple gases to be used, switches from one gas to another, wireless (and wired) air pressure, air consumption rates and even heart rate monitoring. So these are the bells and whistles, but what about reliability?

Along with the advancement of features, dive computers evolved in their reliability as well. The early computers had mechanical on/off switches and several areas where water could infiltrate the computer causing a flood and a rapid failure. There have also been developments in battery technology. These amount to better overall reliability and fewer failures. Nothing is “bullet proof” so you will continue to hear people claim that computers fail, but so will your GPS, your car, and your phone. What needs to be considered is how often they fail, and with dive computers, it is not often.

The question you want to ask yourself is, do you want to learn with the most modern equipment that comes with the additional safety, features and benefits built in or… do you want to learn the old way which you will have to practice more often or get retrained on every time you want to dive? Why do I say retrain? If you learned using the tables, try this exercise. You do your first dive to 16 metres/54 feet for 25 minutes; you saw something during that dive you really want to see again so you plan your next dive to 15 metres/49 feet for 30 minutes, what’s your surface interval?

Go out, enjoy your dives, have fun and do it often, and leave the complicated planning part to the dive computer manufacturers and the technical divers (they love writing everything out on slates).

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20 replies
  1. Dalelynn Sims
    Dalelynn Sims says:

    While I cannot argue that computers are an advancement over the square dive calculations accomplished on most dive tables, knowing and understanding the tables as well as your computer makes one a safer diver I believe. If you understand the tables then you have a better understanding and expectation of what the computer accomplished for you. I have seen to many divers just take it for granted the computer is right and go only by what it says. I have also had more than a couple computers fail on me. Additionally many divers just do not understand the basics for them e.g. I am at 54’ and look at my computer and see it has failed for whatever reason . . ..my dive watch indicates I have only been down for 21 min and I know my air consumption rate therefore although the dive is over I have plenty of time to get with my dive buddy, show them what is wrong, get back to the anchor line and even do a safety stop. I have not exceeded the NDL based on tables/ computer or my consumption rate for the time down. How many divers that are taught to just dive computers are looking at all these things. All things we cover as part of learning both tables and yes computers. I wish it were more.

    • Tom Whelchel
      Tom Whelchel says:

      Yes ! I thoroughly agree. Spot on. Like you, I also learned from ” The Tables” . In fact I used to carry them with me everywhere and would imagine dives in my head and try to remember certain allowable times at such depths etc. It was fun. Memorizing them was essential to me, and I still find myself 26 years later testing my memory. As in many things mastering the BASICS is really important, after that we can develop our own style.

  2. Richard Taylor
    Richard Taylor says:

    100% agree with Sean! A great article! Learning to dive should use the best tools for the job, and diving with a dive computer offers better controls for both the diver and operators. Tables definitely have their place but not at OWSD or AdvAdv levels!! Another reason I have enjoyed teaching SDI since 1999!!!

  3. carlos
    carlos says:

    Dalelynn is correct and there is no reason at all not to teach tables while using computers in a class. Teaching fundamental basic knowledge and theory is NOT going back to the stone age or whatever ridiculous analogy you want to make it is simply giving a student the basic understanding of Diving physiology and theory so when using their computer (if they have one) they have a solid understanding of what it is doing and why and how it is an advantage over static tables.
    BTW, not all divers have or can afford a computer and there are times when a computer breaks down or isn’t available and they need to know how to plan and execute their dives by the standard tables. Not teaching this is simply not preparing a student to be a safe competent diver in all situations and for situations that they may need to use an alternative to a dive computer.
    There is not question at all that a dive computer is by far a better way to dive and there is no comparison there but to use that as a flimsy excuse to not teach tables is just that a flimsy excuse.

  4. Gino Keller
    Gino Keller says:

    Man muss nicht immer das Neuste und das Letzte in eine Ausbildung aufnehmen. Aber die Tabellen sind mehr als ein Steinzeitrelikt! Seit vielen, vielen Jahren gibt es gute und zuverlässige Tauchkomputer (ich tauche 34 Jahre lang). Das Schulen von Tauchtabellen gehört nur noch in Spezielsegmente und nicht in die normale Ausbildung! Dafür sollte eine praxisorientierte Ausbildung mit den Tauchcomputern erfolgen. Das Wichtigste währe, wenn alle Taucher das Angezeigte richtig interpretieren könnten. Speziell bei Vieltauchern die regelmässig von der Mitte ihrer Ferien immer kleine Dekozeiten einfangen. Viele erschrecken sich, handeln falsch oder ignorieren die Anzeige. In diese Richtung müssten die Verbände die Ausbildungsunterlagen anpassen.

    Der Computer ist nicht mehr wegzudenken (ist auch gut so) aber diesen vernünftig einzusetzen die Daten richtig und sicher zu Verstehen und danach zu handeln sind die primären Ziele für ein sicheres Tauchen der Massen! Für die Schwarzmaler unter den Computernutzern sollte auch ein Notfallmanagement bei einem Ausfall in die Ausbildung einfliessen…. dies ist wohl der einfachste Teil da im Buddyteam getaucht wird (sollte), hallte dich einfach an die Angaben von deinem Partnercomputer 😉

    Viel Spass GIK.ch

  5. Sandra Clopp
    Sandra Clopp says:

    Good article and I also agree with what Dalelynn says. It’s important to know what the computers are based on in case they do fail. Although the tables are in the appendix of the OW manual they should not be overlooked by the instructor. I would be doing my students a disservice if I let them pass a class that gives them the qualification to look after themselves under water if they didn’t understand the tables the computer calculates dive times from. They are not completely archaic; the algorithms in the computer are constantly recalculating the information the tables are based on. Also what happens when someone shows up to dive and they don’t have a computer? It’s easy to tell them to not dive deeper than the instructor or divemaster who does have a computer but they also need to be aware of about how long they can be at a given depth. http://www.urbanmanta.com

  6. Jonathan Cross
    Jonathan Cross says:

    Computers have their place but telling people to rely on them alone without knowing or planning more is a scary concept. Computers are not allowed in the commercial industry because they do fail.

  7. Peter Sotis
    Peter Sotis says:


    How refreshing to see an instructor post something in public that goes against the norm in training today. Training standards need to be revamped based on current information and equipment with a realistic approach to application.

    If anyone could show me the statistical proof that someone diving tables is less likely to get bent or run out of gas vs. someone on a dive computer I would support the use of tables. The fact is, there is no such proof. Its also very likely that computers are more likely to assist people from getting bent by keeping better track of their NDL and Deco in real time.

    Some people have no imagination so they stick to what they like to refer to as “old school” philosophy. To me, “old school” refers to the days when we did not know any better and had to guess a lot. “old school” should stay where it is…in the past.

    Facts are, when you teach someone tables, it is the least retained information in the class and it is also the least applied. So if an instructor thinks he is teaching something that will have long term benefit to his student, he is just fooling himself and the student. Spend time teaching your students something that have value…you only have a brief amount of time with them, so make the most of it.

    There is benefit to knowing tables, deco theory of many kinds. That information should be available to those who want to learn and intend to apply it. Start teaching tables and deco theory as a side class so you are getting through to the people that really want to learn. The rest can go diving with computers and enjoy diving for what they want it to be.

    Peter Sotis
    Add Helium, LLC

    • Larry Molnar
      Larry Molnar says:

      Wow, where are you getting your information? While I thoroughly believe computers are safe and dive with 2 at all times, you want to see statistics that are easy to find. In terms of incidence of bends, statistically speaking the US Navy tables are still the safest thing known to man. But statistics don’t tell the entire story, and if that’s what you base everything on you will eventually find yourself being very wrong.

  8. Ian Johnson
    Ian Johnson says:

    I must agree with Sean and Richard. I got my first PDC in the mid 80s, an Orca, and have never used tables for recreational dives since.
    Glad to see that the more traditional certification agencies are catching on.

    • Larry Molnar
      Larry Molnar says:

      By the way, Orca computers had an incidence of bends more than 3X dive tables. Might be one reason they’re out of business.

      • Sean Harrison
        Sean Harrison says:

        Larry, not that I know the whole story, but Orca was made right down the street from where I got my start in the dive industry. From memory, one of the reasons they had a “high” incident rate, was the on/off switch. This was commonly know as the “clear my dive switch”. Divers would either deliberately or accidentally switch the unit off, which cleared all residual gas information, and then turn it back on. The old days of technology where Orca was trying to fix one problem, battery length, and created another one.

  9. Don G.
    Don G. says:

    I agree that computers have made diving better. You can’t argue that the profiles provide more flexibility. I take issue with the idea that the tables are unnecessary in Basic OW. I was on a recreational dive with a group. The planned max depth was 65′. At 57′ my computer flooded. Using my analog air pressure gauge, my wristwatch and staying above the DM, I completed the dive and even though I had stayed well above him, I used his max depth for my planning. Afterward, I borrowed an analog depth gauge and using the tables, I finished a fine week of diving. I wouldn’t be able to do that using a new computer because the info from my first dive wouldn’t be in there.

  10. Ian Johnson
    Ian Johnson says:

    Like Don G I had a computer flood on dive 1 of the day while on a 7 day live aboard trip. I had a back up computer.
    I did the same thing as Don however then used the back up unit. I just stayed above my max depth all day. Next day I just dived as usual.
    In the early 90s I used to lead groups with the depth and bottom time worked out on my computer regardless of what the guests used. I remember many saying ” wow I checked my tables after the dive and was way over my allowed bottom time “.
    These things are great.
    I agree that we should teach tables at OW level as a historic thing as well as using them to help explain how computers work.

  11. FCE
    FCE says:

    So let’s stop teaching spelling as the computer will simply fix any errors for us. This debate extends beyond diving. Having been at sea when the GPS failed, it was good to be able to shoot stars and determine our position the old school way using the nautical almanac and sight reduction tables. Electrons will fail at some point. I love my Petrel and V-Planner, but I made sure that my son knew how to use the tables when he started diving. Bottom line, teach the tables both for their historic value and as a back up.

    • anon4now
      anon4now says:

      As a relatively new diver (about 1 year <20 dives since I did my OW). I couldn't agree anymore with you, FCE. I learnt on a computer with reference to tables, but no real comprehension of them, plus they also seems like a fuzzy memory. Sure they're complex, but frickin' important, and in the days of "old school", you had no other choice; you either learnt them or didn't dive. I'd revel in the opportunity to learn them comprehensively, so much so, I'm actually considering redoing my OW with an agency/instructor willing to be patient enough and knowledgeable to teach me. As has bee mentioned earlier by others, I understand having tables as a backup to my computer in case of failure etc. Computers can be great at being more flexible with your actual dive; that is until it stops working as it should (much like my phone is whilst trying to write this reply). But without the backup tables you're in trouble.

      I recently did a dive on holiday with "full" hire gear*, in which I got a depth and air SPG – no computer, no watch, no compass. I Knew that staying above my DM guide (whom did have a computer) should mean I'd be alright, unless they f'd up. But this was inadequate.

      *The number of times I've been out on a boat and you're left to figure out how to use the dive computer by yourself (which as a different computer, operates completely differently to the previous kit you've used before) is shameful! If you're leasing/lending kit, you've a responsibility to show people what they're actually getting, that it works and how to use it; end of! Which is why I'm never going back to those operators and when I get to a PC I'll name and shame in my review of them on trip advisor etc.

  12. Jamie King
    Jamie King says:

    I’m only talking about recreational diving here.
    I learnt on tables, dives were shorter as we worked out the dives on square profiIes. I now dive with two computers, an air integrated one as my main, and a cheaper back up. Both do nitrox, and I still have my spg. I can even plan my depths and dive times on them!
    My dives are now longer, more enjoyable, and simpler. I still have two points of failure, four if you count my buddy. What happened if your tables were lost underwater, did you carry two?
    Tables have their place, it’s good to understand the theory, but they are no substitute for a dive computer in modern times.

  13. Lance Velez
    Lance Velez says:

    Computers are good but not everybody can afford one especially those just starting scuba training. Tables are an inexpensive way to plan dives and learn the basics of planning dives without being dependent on a gadget.


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