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Thread: Plan your dive and dive your plan ...

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    Site Moderator Grateful Diver's Avatar
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    Default Plan your dive and dive your plan ...

    As someone who teaches scuba diving, one of my pet peeves has always been the tendency of some instructors to tell students what they should do while at the same time neglecting to tell them how to do it.

    "Plan your dive and dive your plan" ... we've all heard it, but what does it really mean?

    At a conceptual level it implies that before getting in the water, you should have an idea of where you're going, who you're going with, how long you're going to be there, and how you're going to get back.

    It's no different, really, than taking a trip in your car. You usually don't just jump in the car, drive around, and head back when you feel like it. You have a purpose, and you ... at some level ... plan before you go how you're going to use the car to achieve that purpose.

    With diving, "planning your dive" at a minimum should involve determining how deep you want to go, how long you intend to stay, and how much air you will need in your tank when you begin your ascent. "Diving your plan" means, simply, that once you've determined the above ... impose enough self-discipline on yourself to stick to what you had decided to do.

    "End the dive with 500 psi" ... that's another one of those things they always tell you without giving you a clue how to do it. Well, it's also part of dive planning, and you should be thinking about your air supply before you ever get in the water ... not waiting till you're swimming around and thinking about how much you want to have when the dive's over.

    Gas management is one of the most important skills not taught by the major agencies. You would never consider taking your car across a wilderness ... knowing that there are no gas stations along the way ... without having a pretty fair idea of whether or not you had enough gas to make it. And yet that's exactly what scuba divers often do when they jump in for a dive without knowing how much air they breathe, on average, and whether or not the air in their tank is sufficient for the depth they plan to go to ... or the amount of time they intend to stay. Think about it ... the air in your tank is all that you will have available until you get back to the surface ... wouldn't it be great to be assured that you're not going to run out before you've completed your dive?

    There are straightforward ways to determine that ... although at first it involves some measuring and some arithmetic. Once you know your consumption rate, though, you can actually plan a dive based on the amount of air you HAVE ... rather than having to abort the dive when you notice your pressure gauge getting low.

    Many divers get really fascinated with depth ... some chasing "personal best" depth records without really understanding either the risks involved or the preparation needed to go to that depth safely. Understanding how much gas you consume, and how that consumption relates to depth, will help you determine whether or not your depth goals are realistic ... or even safe. It's all part of the "plan your dive" thing.

    I use a rule of thumb for my new diver students ... don't go deeper than the cubic feet of gas your tank will hold. In other words ... if you're diving an AL80, limit your dive to 80 feet. Sure, you CAN go deeper ... but it'll be either a short (bounce) dive or you'll be risking running out of air before you can complete your ascent safely.

    Planning your dive also involves considering your own skill and training level, and that of your dive buddy. Ask yourself if it's adequate for the dive you want to do. What's your comfort level in the water? Can you hold a safety stop without having to hang onto something? Do you need to kick your fins in order to hold your position in the water? Are you comfortable in current ... or surge? Make sure you get some information on the type of conditions you're likely to encounter, and ask yourself if you're ready for those conditions ... and be honest with yourself, because we all have a tendency to think we're more skilled than we actually are.

    Another part of planning ... how am I getting out of the water? Am I diving from a boat or from a shore site? If a boat, do I need to get back to the anchor line or can I just surface anywhere and the boat will pick me up? If from shore, do I need to exit at a particular place? What kind of hazards (e.g. current, waves, boat traffic) might I anticipate on my exit? All of this must be considered in the "plan your dive" phase ... never get into the water without first having determined how you're going to get out.

    Planning your dive, really, means thinking about all of those things. Determine ... before you ever get in the water ... what type of dive you want to do, and ascertain that it's within your capability. Consider your skills and equipment, and those of your dive buddy, and determine that they are adequate to do the dive with a relative amount of safety and comfort ... diving's all about having fun, after all ... and terrorizing yourself with the unknown isn't much fun for most of us.

    Diving your plan is the execution part ... don't go deeper, don't stay longer, don't go off on a whimsical junket ... and begin your ascent when your gas plan had determined that you should. There's a great peace of mind that comes from knowing ... because you thought about it in advance ... that you can safely handle the dive you're doing. It helps you relax ... and that helps you enjoy the dive more. And enjoyment, after all, is why we dive.

    ... Bob (Grateful Diver)

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    Senior Member dherbert's Avatar
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    Thanks for posting. That's another post from you that will end up as a hand out for my students. Keep em coming!
    Less BS, More BT

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    Senior Member drbill's Avatar
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    As a diver primarily interested in marine life, I recognize the value of your advice to new divers and those whose diving permits a plan to be employed. However, in my case, my dive plan is dictated by what I encounter underwater, not by any preconceived "plan." It is Mother Nature that dictates things for me and she just ain't that predictable.

    I may be "planning" a dive to film deep water brachiopods at 150-200 ft, but encounter an unusual find (such as a recent thornback ray, the first I'd ever seen off Catalina) and end up filming at a depth of 110-120 ft much of the deep portion of my dive. Or I may be "planning" to film a moray I know is usually seen in a hole at 40 ft, but find it is absent that day so I end up filming bat rays at 70 ft.

    Of course my diving is not necessarily typical of that others engage in. However, it is much easier to "plan" a dive to visit a wreck at 70 ft which hasn't shifted more than a few feet over time. When one has fixed goals in mind for the dive, plans are much easier to adhere to.

    With that said, I don't recommend that people skip planning their own dives... just that it depends very much on the goal of the dives. Certainly newer divers need to develop the experience and practice before they know enough to do effective gas management and dive more flexible profiles. The most important part of MY plan is to have enough gas and redundancy to engage in any potential dive profile regardless of where I may end up filming.

    I've spent years "learning" my profile limits and "learning" how to manage my gas for a wide range of different ones. I used to make a "game" of planning for my max depth and dive duration on two separate dives with one HP120 fill, then adjusting my profile to dynamically accommodate those goals. This is experience new divers won't have accumulated.

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    Site Moderator Grateful Diver's Avatar
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    Quote Originally Posted by drbill View Post
    As a diver primarily interested in marine life, I recognize the value of your advice to new divers and those whose diving permits a plan to be employed. However, in my case, my dive plan is dictated by what I encounter underwater, not by any preconceived "plan." It is Mother Nature that dictates things for me and she just ain't that predictable.
    ... that's the reason I placed this discussion in the "New to Diving" forum ... it is directed specifically toward new divers. Clearly, I don't need to be talking to people with thousands of dives about how to plan (or choose not to plan) their dives.

    I would like to encourage discussion from our more experienced divers in a manner that those just getting into diving can relate to ... because most of us acknowledge that the current state of training leaves some knowledge "gaps" that must get filled in through other means ...

    ... Bob (Grateful Diver)

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    Quote Originally Posted by Grateful Diver View Post
    ... that's the reason I placed this discussion in the "New to Diving" forum ... it is directed specifically toward new divers. Clearly, I don't need to be talking to people with thousands of dives about how to plan (or choose not to plan) their dives.

    I would like to encourage discussion from our more experienced divers in a manner that those just getting into diving can relate to ... because most of us acknowledge that the current state of training leaves some knowledge "gaps" that must get filled in through other means ...

    ... Bob (Grateful Diver)
    Bob: IMO, your original post is "spot on". I like your "rule" about depth and tanks-AL80 to 80 fsw. I have violated this rule multiple times and,currently, am using double 50's for deeper dives. I always learn from these posts.

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    Bob,

    You gotta' get a website, really. Yahoo will put you on the web for $5.00 a month, you get plenty of pages. Get your photo up (Catherine can take it: you in a wetsuit, on the bow, wind-swept hair). Then, we fellow posters will promote the site, you'll get linked by admiring instructors everywhere. Then, NAUI Sources magazine will ask you to publish. Then, you reluctantly run for NAUI Board of Directors, get elected by a landslide!! (Remember, awe-inspiring website). And t-h-e-n... you put PADI out business.

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    Site Moderator Grateful Diver's Avatar
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    Quote Originally Posted by daniel f aleman View Post
    Get your photo up (Catherine can take it: you in a wetsuit, on the bow, wind-swept hair).
    LOL - that would be quite a feat! I'm afraid it would require a bit more than Grecian Formula, though ...

    ... Bob (Grateful Diver)

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    Senior Member dherbert's Avatar
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    Wind swept facial hair, maybe?
    Less BS, More BT

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    Senior Member mwhities's Avatar
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    I'm sure I could host you if you were interested Bob. Let me know.

    Michael
    No sig here.... yet.

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    Quote Originally Posted by Grateful Diver View Post
    Gas management is one of the most important skills not taught by the major agencies.
    I don't know that it's not taught, but it is taught at a very basic level.

    I think one of the reasons for this, though, is that new divers' really have to experience diving for some time before gas management starts to make sense, and before their consumption rates start to level off.

    I've only got 28 dives under my belt, and I still vividly recall being a newb in the pool for the first time just this last April.

    My first 15 "real dives" had basically the same profile, and my gas consumption varied dramatically across them, even on 2 dives at the same site on the same day to the same depth my sac rate varied by a significant amount.

    As a new diver, I understood sac rate and gas management conceptually, but I am still not to the point where I can count on my gas consumption to be a predictable variable.

    You would never consider taking your car across a wilderness ... knowing that there are no gas stations along the way ... without having a pretty fair idea of whether or not you had enough gas to make it. And yet that's exactly what scuba divers often do when they jump in for a dive without knowing how much air they breathe, on average, and whether or not the air in their tank is sufficient for the depth they plan to go to ... or the amount of time they intend to stay.
    Then for someone like me, how would you suggest I actually plan that? Take my worst 5 dives and plan for them? But 3 of those are very early in my log book. Take my average? A moving average of the last 5 dives of similar profiles? How similar is similar?

    The reality is, for at least some divers such as myself, experience is not just about feeling what it's like to get wet, it's also about learning how to breath and how to move efficiently, and the experimentation I engage in in getting that knowledge so drastically effects my gas usage that I simply have no viable data to go on when it comes to gas planning.

    It is precisely through getting experience that I will gain that data, and once I have the data, then I might well be able to make meaningful plans. But as it is, to use your analogy, I'm driving with no map and only directions that I should "go that way a bit."

    And that's fine. Sometimes that's the best you have to go on.

    There are straightforward ways to determine that ... although at first it involves some measuring and some arithmetic. Once you know your consumption rate, though, you can actually plan a dive based on the amount of air you HAVE ... rather than having to abort the dive when you notice your pressure gauge getting low.
    It's not that easy for beginners who have great variability in their gas usage due primarily to inexperience.

    I'm a statistician by trade, I can do the math. My problem is that the variability I demonstrate dive to dive and day to day is so great as to make drawing a supportable conclussion on a mere 28 dives impossible.

    Maybe when I get to 50 or so, I'll have decreased the variance enough to be able to engage in meaningful gas planning. But as of today, it is an exercise for the sake of the exercise and provides no useful information for planning purposes.

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    Site Moderator Grateful Diver's Avatar
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    Actually, Kingpatzer, you are doing exactly what this thread is meant to get new divers doing ... thinking about it.

    A surprising number don't, which isn't their fault ... they were never taught that they were supposed to.

    If you were taught about surface air consumption in OW ... to the point where you understand the principles ... you had way above-average instruction.

    Everything you say in your post is dead nuts on ... excellent comments. Exactly the sort I was hoping to inspire in this conversation. But keep in mind the bigger picture ... gas management is but one aspect of dive planning, although it's an important and often overlooked one.

    To address one specific question ...

    Then for someone like me, how would you suggest I actually plan that? Take my worst 5 dives and plan for them? But 3 of those are very early in my log book. Take my average? A moving average of the last 5 dives of similar profiles? How similar is similar?
    Look at every dive ... as a statistician you will KNOW what you're looking for ... trends. If you have a way to track the average depth of your dive, and you understand the basic principles of calculating SAC, it's simple to look at your average consumption for every dive. It will always vary ... but you're right that as your experience increases, the variability from dive to dive will become less. Look at your average consumption on each dive. Ask yourself what factors drove it higher or lower than the previous dives. Eventually a pattern will start to become evident ... one that will allow you, based on the conditions you anticipate in your plan, to choose a consumption rate that makes sense for that dive.

    This is little different than what experienced divers do when planning technical dives. They don't choose a number based on their ACTUAL consumption ... they choose one slightly higher than what they think it will be ... because they know that variable conditions will have an impact on their actual usage and they plan for worst-case.

    That can work, even on a reef dive ... even with a very inexperienced diver.

    Maybe when I get to 50 or so, I'll have decreased the variance enough to be able to engage in meaningful gas planning. But as of today, it is an exercise for the sake of the exercise and provides no useful information for planning purposes.
    I think every single person who's ever been through my AOW class would disagree with that statement. Going through a gas planning exercise will change the way you think about dive planning ... whether or not the information you derive the first few times you do it prove to be as accurate as you'd like it to be. And THAT, really, is the point of the exercise ... to get you thinking about it BEFORE you get in the water ... rather than reacting to what your SPG is telling you.

    ... Bob (Grateful Diver)

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    Junior Member uwslate's Avatar
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    Thanks, Bob, for your reminder. I have 47 dives in a wide range of conditions/depths, was out of the water for a good decade until recently, and know that (statistically) I am in the group of divers most likely to die.

    I am fanatical about planning my dives and diving my plans. I also have called three dives in the past two months, each under very different circumstances, to err on the side of caution--and I've not been sorry once. To rephrase Bob Marley, "She who dive and run away/Live to dive another day!"

    uwslate

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    Site Moderator Dive-aholic's Avatar
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    Another grate write up, Bob! I've implemented gas management into my dive courses and even provide rock bottom pressures to students and most divers diving with me. This should be a universal thing.
    Rob Neto
    Chipola Divers - Recreational, Technical, and Cave Diving Instruction & Mentorship

    "Survival depends on being able to suppress anxiety and replace it with calm, clear, quick and correct reasoning..." -Sheck Exley

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    Member annasea's Avatar
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    Great information, Bob! I was especially intrigued by the following as I had never heard it before...

    Quote Originally Posted by Grateful Diver View Post
    <snip>
    I use a rule of thumb for my new diver students ... don't go deeper than the cubic feet of gas your tank will hold. In other words ... if you're diving an AL80, limit your dive to 80 feet. Sure, you CAN go deeper ... but it'll be either a short (bounce) dive or you'll be risking running out of air before you can complete your ascent safely. <snip>
    I do have a question, of course! What about all those wreck dives done in FL, for example, where divers are renting tanks from the dive op? From what I've seen in my albeit very limited exposure to boat diving, most/all rental tanks are AL80s, yet aren't plenty of wrecks deeper than 80'?

    I dived the Captain Tony last month out of Boynton Beach to a maximum depth of 87' (most of the dive was probably under 80' though) and used an AL80. Good to know the reason my dive was short (37 min.) was probably due more to compressed gas than poor air consumption.

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    Site Moderator Grateful Diver's Avatar
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    Quote Originally Posted by annasea View Post
    Great information, Bob! I was especially intrigued by the following as I had never heard it before...



    I do have a question, of course! What about all those wreck dives done in FL, for example, where divers are renting tanks from the dive op? From what I've seen in my albeit very limited exposure to boat diving, most/all rental tanks are AL80s, yet aren't plenty of wrecks deeper than 80'?

    I dived the Captain Tony last month out of Boynton Beach to a maximum depth of 87' (most of the dive was probably under 80' though) and used an AL80. Good to know the reason my dive was short (37 min.) was probably due more to compressed gas than poor air consumption.
    Yes, people do it all the time ... and as long as nothing goes wrong, you'll get a dive out of it ... although it will probably be a short one (especially for newer divers who typically have high consumption rates). But if something goes wrong and you end up having to share gas, you most likely won't have enough to come up at a safe rate.

    Think on this ... if you and your dive buddy are both using AL80's on a deep dive, and one of you runs out of gas, how much gas do you think it's likely the other buddy's gonna have to share?

    Chances are he or she's gonna be pretty low, too ...

    ... Bob (Grateful Diver)

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