Do you Plan your dive or Dive your plan within NDLs?

[Bennno]

Is this considered a Plan your Dive?

Sure, why not? As long as you have a max depth and a turn pressure, that's an OK plan.

 

[Rusty Roo]

So for shallow dives - less than 33 meters / 100 feet - is it acceptable to jump in without a plan? As long as you monitor your PDC and SPG/AI? (I will assume for this scenario you should have an idea on turn pressure or rock bottom.)
Is this considered a Plan your Dive?

yeah if zodiac pick up just keep on swimming pop smb get scooped up. if going back to a certain point, 100 bar turn.

 

[tbone1004]

yes, you have limits that can't be broken, they are depth, air, time.
If you know that you will run out of gas before you hit NDL's, and you calculated rock bottom, and there is a hard floor, the dive plan is "we're going to poke around until we hit our gas limit*.

 

[Storker]

If you know that you will run out of gas before you hit NDL's, and you calculated rock bottom, and there is a hard floor, the dive plan is "we're going to poke around until we hit our gas limit*.

If I'm diving with my regular buddy, that's usually good enough, because we've dived together so many times that everything else is either "follow established practice" or given by the site and our expectations. If I'm diving with a new(ish) buddy, I like to go through a few key points, like:

• In what direction are we starting out?
• Do we want to go fast or slow?
• Is there anything one of us should look out for, e.g. should I - or you - pay attention to whether or not you - or I - are narked when we reach some 30-ish meters?
• Who'll be (mostly) leading, who'll be (mostly) following?
• If there's a sloping bottom, what's our planned max depth and contingency max depth?
• Are our primary purpose harvesting (e.g. scallops), looking for cool critters, hunting, or something else?
• Are one of us - or both - going to shoot a dSMB at the end of the dive?

And due to the way we dive here, we also have to have an idea of our max run time before the dive leader is allowed to worry about whether or not we'll surface before our gas runs out.


My point is that quite a few of the things a lot of us take for granted after a few dives and don't think about, are in fact a kind of unconscious dive planning. We're just not necessarily aware that we're doing it.

 

[oldschoolto]

Most of the diving done by the wife and I don't need a "PLAN"... 30' - 50' dive in a cold lake in wet suits... We get cold before we get close to running low on gas, or go into deco... Spend plenty of time in the boat warming up before the second dive, equals good off gassing...

Diving warm water reefs of bonaire... We head out and drop down to 60' - 70' swim up current and turn at half gas and move up to 30' - 20' feet on the way back.... Then spend 5 to10 minutes or so playing at 10' looking at critters... Then a good 1 - 3 hour surface break ... 3 dives a day max....

The only dive that we sit down the night before and " PLAN " is the hilma hooker wreck.... We spend time laying the plan of what we are going to do and how we are going to deal with things that may come up.. We lay out the gas plan and depths... And we stay out of deco, but have plan to deal with it...

So, 95% of our diving is done running Navy tables and the 60/60-120 in my head, With a depth gage and timer... When I plan the wreck dive, I also use the 60/60-120 rule... My wife has a VEO 1 and I have never made her computer beep..

As I said before, I have boughten VEO 3 computers for the wife and I .. So I'll be diving the computer in Bonaire in a few weeks... It's a 14 days of diving trip... We will see how it goes...

Jim....

 

[boulderjohn]

Count me among the people whose head is hurting--and I only read half the posts.

When I am teaching gas consumption, I tell students that a lot of different people in a lot of different agencies use a lot of different terms in a lot of different ways. I tell them that when they get together they tend to argue that the correct definitions of those terms are the ones they were taught, and people insisting on the different definitions they were taught are dead wrong and worthy of eternal scorn.

So I just teach them the main idea, call it all SAC, and tell them to adjust to whatever terms other people are using and don't argue.

 

[guyharrisonphoto]

For NDL diving, my planning is to set the general parameters of the dive and let the computer do the real-time calculations during the dive..

I program my mix into the computer which establishes the max depth based on O2 toxicity. This is done for each dive.

I determine my desired NDL by selecting a computer running an algorithm that suits me, and setting my desired conservatism level on the computer. This, of course, is only done once.

For gas planning, I determine my desired surface reserve (i.e. the gas available to share with my buddy in an emergency) based on the dive depth and expected conditions (current, etc) and I program that reserve into the computer. IF I am on a dive that calls for a turn pressure (no for drift or hot drops on wrecks, but yes for shore and anchored boat dives), I also set the desired PSI for an alert on the computer. This is not necessarily done every dive, or even that often. I typically leave the reserve at 500, but will bump it up if I am diving deeper than 90 feet or expect a hard physical dive (current, surge, etc).

Based on this, the computer will calculate and show my max depth based on the mix, my NDL remaining, and my gas time remaining with a turn pressure alert if needed, all based on the real-time conditions of the dive. So, the planning is done when I set up the computer, the computer is used to execute the plan.

 

[drbill]

Being a marine biologist, I rarely put together a pre-dive plan. My dives are largely determined by what I encounter in the way of critters. Certainly in the past when I was diving to depths in excess of recreational limits, I would often exceed NDL if subjects kept me at depth for any length. Of course I carried plenty of gas (both inside me and in my tanks). Today I rarely dive below 100 fsw locally, only when I'm at a remote destination. However, it is rare that I exceed NDL limits these days since I strive for bottom time to gather more video footage or study my subjects longer.

 

[tursiops]

I happen to use an excel sheet that uses my avg SAC (last 100 dives), is based on the Naui tables (multi level dive or dives), I plug in depth and time and excel spits out the total gas and total time requiem for the dive including descent, ascent and safety stops.
I use it as a pre-plan and use my PDC and spg to validate my dive.

I'll say it again: it is dangerous to use NAUI or any tables NOT designed for multi-level dives, to plan a multi-level dive, unless you use it as just rough guidance and then actually dive by your computer.

 

[tursiops]

I've read all the posts in this thread (not sure why....), and my conclusion is this:

• We figure out how much gas we use by measuring pressure loss per time, at some depth.Call it at-depth pressure/minute.
• To have useful number at all depth, we convert it to surface pressure/minute.
• This number is only useful in planning if we dive the same size tank we did the measurement with, but I don't, I variously use (imperial units because that is how they are marked) a 63, an 80, a 95, double 100's, whatever.
• So to have only one number to remember, and to use in software and in discussions with other divers and on forums, I convert that surface pressure/minute in a specific tank to a surface volume/minute. THAT is my whatever-you-want-call-it....I call it SAC, but that does not really matter.

Punch line: you can use your pressure/minute rates all you want, but unless the tank you are diving is always the same size, you need to do more than rely on that number.

By the way, I really don't care whether it is imperial or metric units I use; I'm conversant with both (apparently unlike many posters here!), each has their advantages and disadvantages.
But I DO CARE if people insist on their personal definition of some term when clearly other definitions exist.