Limits: what they are, why they are important and how to establish them

[Akimbo]

A couple of years ago I talked about this very thing with one of my students, who was looking back on a lifetime of rock climbing...

The "young male and cocky" diver problem was well recognized in Navy First Class Diver school, which is partially training to be a diving supervisor. It is especially important during rescue operations where sailors will do really high risk things to save shipmates. The "invincible" don't stop to analyze that they could make the problem worse by requiring rescue themselves... or be a body recovery. I was unusually young for that school and it probably helped keep me alive. This post alludes to how central the leadership training is in the course.

If fact, the opening scene of the film Men of Honor was the poster child for the issue.

 

[Coztick]

@The Chairman (and others), being new to this we (my daughter and I) are learning tons all the time. In part to the reading I do on SB.

Question for you/others: where does experience begin to substitute for formal training in some form or fashion and how do you know? As an example, I see folks on SB that have tons and tons of dives, have an OW certification only, and do deep(er) dives all the time. I suspect they feel quite comfortable at the increased depths (past their formal training of 60') and I suspect they have (or feel they have) plenty of experience to enable their comfort and knowledge to dive that deep.

My daughter and I are just beginning this new adventure (diving). Our typical reef dives we go on are 60'. I have had her sit down at the dining table with me and do detailed dive planning calcs (calc'ing air usage based on RMVs for the dive, an issue, a return, a safety stop, etc.) mainly so she understands these things are not arbitrary and she understands the concept. Our dives have been drift dives for the most part so we haven't had a "return pressure" as much as we just have a "ascent pressure" where we end the dive and just go up. We have used return pressure to a slight degree when doing shark tooth diving in the Gulf, but the waters are very shallow and you really aren't venturing too far from the boat, we just made our returns early but basically kept searching for teeth... just changed our heading to return towards the boat. I think we'll do a wreck dive or more anchored dives this Spring so we'll get an opportunity to employ more planning relative to turn/return pressures etc.

For us, we don't plan (or have business) on doing deep (to me that means 90' plus) dives any time soon (due to lack of experience and training IMO). That said, if we were presented with the question of diving to 70' (or not), I don't think I would hesitate. I feel comfortable with both of us diving to there - is that bad? Now... if presented with diving to 80' by a DM, I would respond with - we have only dived to "X" feet (whatever that is... it's "60" right now) and would only dive to that depth if you (DM) are ok with us sticking with you on the dive and you are ok keeping an eye (buddy-style) on us - is that bad? Admittedly, we are new to this, and hence ignorant to plenty of things relative to diving. So we don't know what we don't know. And that's where more training and experience comes in. But right now, the above would be my approach - again, is that bad? Speak freely, I take no pride in this matter and don't have an ego to hurt... I'm ignorant to plenty of things diving.

I think it's fantastic that you and your daughter can share scuba.
It sounds as though you both have all the basic skills to enjoy most recreational dives...as long as nothing goes wrong.
Between ow classes and experience should be practice.
Beyond planning a dive you and your daughter should be talking about crisis management. Remember, we are playing in a lethal environment. Do your buddy checks, do uw drills in shallow water until you can do them upside down while maintaining depth.
If your buddy team can handle any crisis with no stress, then your probably ready for anything recreational...assuming no current and good visability.
That Ieads us to the possibility of buddy separation and the need for self reliance...
Just sayin'.

Happy diving, Kevin

 

[1000RR]

I think it's fantastic that you and your daughter can share scuba.
It sounds as though you both have all the basic skills to enjoy most recreational dives...as long as nothing goes wrong.
Between ow classes and experience should be practice.
Beyond planning a dive you and your daughter should be talking about crisis management. Remember, we are playing in a lethal environment. Do your buddy checks, do uw drills in shallow water until you can do them upside down while maintaining depth.

Many times we discuss things from crisis management to dive planning on the car ride to/from diving (2hrs ea h way). Or we discuss things particular to the dive we're doing that might be different than we've experienced before. That said, being things are new to me too, I won't know ALL the things we could/should probably discuss. We do make the effort though and as time/experience goes on I'm sure we'll learn more of the intricacies that could/should be discussed.

If your buddy team can handle any crisis with no stress, then your probably ready for anything recreational...assuming no current and good visability.

We do dive in current a bit, but with good visibility generally. Our shore dives can be hit and miss on the visibility and our occasional Megaladon tooth hunting is definitely VERY low visibility.

That Ieads us to the possibility of buddy separation and the need for self reliance...
Just sayin'.

Happy diving, Kevin

Can you expand on what you're sayin'? Right now, the plan/approach to buddy separation is to look around you for a minute and then surface if no luck. By "self reliance" are you meaning slinging a pony at some point?

 

[The Chairman]

Beyond planning a dive you and your daughter should be talking about crisis management.

I almost agree with this. However, there is no way to mentally prepare for crisis management. You're fooling yourself if you think you can. You should be discussing crisis avoidance by diving within your limits instead. The best way to handle a crisis is to avoid it completely.

Let me repeat that...

The best way to handle a crisis is to avoid it completely.​

The entire first post of this thread is about just that: avoiding crises by diving within your limits. Can there be "oh crap!" moments out of the blue? Sure. But they are so rare that there's no way to properly prepare for them. It's my personal and professional opinion that %99.9 percent of all Scuba accidents could have been prevented by paying attention to your limits before you splash, while you're underwater, as you ascend, and while you're on the surface. There's simply no excuse for running out of air or running out of buddy. None, nada and squat in precisely that order. There's simply no excuse for horrible buoyancy, trim or otherwise being out of control. If you are prone to these, please get the remedial training needed to prevent these from happening before you dive. Yes, your life actually depends on it. Know your limits. Your limits may very well preclude you from diving until you correct certain skills and/or habits. No, I'm not trying to scare you out of the water but I'm trying to get you to realize that you and you alone are responsible for your safety when you dive. Remember...

The best way to handle a crisis is to avoid it completely.​

 

[The Chairman]

Caveat...

By crisis, I'm referring to an actual crisis. Losing a fin, a mask or an air leak are not crises. At least, they shouldn't be. Training covers most of the "whoopsies" you'll encounter. Training should give you a basket of mental "tools" to work with. It's up to you to perfect those skills and hopefully before you take the next class. Adding new tools without being able to properly use the last ones you got will only confuse you. This is why experience is so valuable. I've dove with DMs who haven't mastered trim or buoyancy and their situational awareness suffers because they are simply struggling with not nose darting into the silt. How you dive is entirely up to you.

Training is important. Choosing the right trainer is even more important. Still, how you dive is entirely up to you.

 

[Akimbo]

By crisis, I'm referring to an actual crisis. Losing a fin, a mask or an air leak are not crises. At least, they shouldn't be.

(Agreeing, not debating. But it is a good setup for my ongoing rant.)
Taking it to the more advanced level, running OOA (Out Of Air) "should" never be a crisis either -- whether caused by a planning underestimate or equipment failure. Carry an in independent backup if you are deeper than you have proven to yourself that you can safely make a free ascent. Free ascents are the worst case option but the surface is the only 100% reliable backup air supply.

Studying diving accident reports beyond very newly trained divers clearly shows that injuries and fatalities are usually caused by a series of fairly innocuous events -- often three or more. I submit that using your buddy's Octo is not a sufficient OOA backup plan alone. Buddy separation AND a getting too distracted to check your SPG should be a life lesson, not a death sentence. Now add a third screw up to your crisis management plan and dive accordingly. Oh, don't forget a serious OOA condition also means you can't inflate your BC.

 

[boulderjohn]

By crisis, I'm referring to an actual crisis. Losing a fin, a mask or an air leak are not crises. At least, they shouldn't be. Training covers most of the "whoopsies" you'll encounter. Training should give you a basket of mental "tools" to work with.

I attended a workshop a couple of years ago that was given by a representative of the insurance industry who said essentially the same thing, but using different terminology. The main idea is that an incident can occur during a dive, but it is not a true emergency or a crisis until that incident is handled improperly. For OW diving, the initial training leading to certification teaches how to handle all incidents properly, so there never should be a crisis or emergency. Those only occur when you handle the incident improperly. They even included running out of air--if that happens, you have been taught what to do to manage the incident. It only becomes an emergency or crisis when you have an improper response, like bolting to the surface while holding your breath.

 

[Slow]

So, take your planned depth, calculate your ascent pressure, subtract it from your start pressure and then divide the remainder in half. That's how much gas you get to use. Subtract it from your starting pressure (again) and you now have your turn pressure.​

Here's a dive to 80ft with an AL80 @3,000psi

80x10= 800psi ascent pressure.
(3000-800)/2= 1100psi usable gas
3000-1100= 1900psi is now your turn pressure

Mathematically equivalent, but I find easier to do in my head:

(Start_pressure + Ascent_pressure)/2

(3000+800)/2 = 3800/2 = 1900

FWIW, I keep 4 numbers in my head for ascent based on rock-bottom calculations with 1 cfm RMV (roughly double normal to account for emergency w/ buddy breathing on octo).

Ascent pressures of 700/800/1000/1200 psi for depths of 30/60/90/120 feet. Easy to recalculate turn pressures on the fly using the (start+ascent)/2 and using those memorized ascent numbers. I've found this approach eases my concern levels during a follow-me DM-led dive.

I'm a little surprised it's not taught this way...it seems a lot easier to me and to the buddies I've talked about it with.

 

[The Chairman]

Taking it to the more advanced level, running OOA (Out Of Air) "should" never be a crisis either

I submit that using your buddy's Octo is not a sufficient OOA backup plan alone

I don't disagree with any of this. However, let's add a caveat for the newer and even older divers who dive with buddies. You are your buddy's spare air, spare mask, spare fins, spare brain and even their spare alarm clock. They should be yours as well. If/when you check your air, do you check your buddy's? WHY THE HELL NOT??? How fast is your buddy consuming their air? WHAT??? YOU DONT PHREAKING KNOW? Again, WHY THE HELL NOT??? Remember the statement I emboldened, enlarged and centered? It went something like this:

The best way to handle a crisis is to avoid it completely. ​

So, when you check your air, check your buddy's too. You don't always have to bother them if you extrapolate. Here's what you do. When you consume your first 500 psi go ahead and bother them. You'll have had to ask them their beginning pressure, and hopefully you did. So, how much did they use? If they used less air than you, then you are the limiting diver. You'll need to turn when your air is depleted. I would still check at half way and 3/4 to the turn, but barring any change like them getting excited over a mermaid or a shark, you should be able to guess how much they have when you look at your SPG. However, if they consumed more than you than it's time to extrapolate and keep tabs on where they should be. Say you both started with 3000, and they used 600 when you used 500. You figured out that on this 100 ft dive, your turn should be @2000 and ascent @1000. What should your new turn be? Round it, They should
be at 2000 when you are at 2200. Is it perfect? No, but it's probably close enough, and if you know your buddy's air pressure, I bet you didn't lose them in the process. See? It's a win/win and nobody ran out of gas.

Take away? Your buddy's limits are just as important as yours are. Be a buddy and act like one.

 

[The Chairman]

Caveat: Buddy can you hear me? Can you hear them?

Probably the best way to stay close to your buddy as well as to keep tabs on their well being is to listen to them throughout your dive. Every diver has a certain rhythm and pitch to their breathing. Some sound like Darth Vader and others more like Mickey Mouse. Everyone is a bit different, so clue into how your buddy breathes. It's not too distracting, and when you hear the tempo increase, you can bet that their excitement has increased. It might be a little or it might be a lot. The sooner you attend to their issue, like a good buddy, the better off both of you will be. This is especially convenient when you're in front. Rather than continually turning around, just listen. Don't hear them? Duck your head down and look between your fins before you turn around... it uses a lot less air.