Triggers of Dive Accidents

[boulderjohn]

Thanks for your input. I had to google "safety sausage," so I guess you can add that to the list of things I wasn't taught or shown in my OW class.

Safety sausages have not traditionally been a part of OW classes in large part because except for certain regions, they are generally new to diving and only recently become used widely. I dived for a number of years before I saw my first one.

Going back to your earlier issues of being low on air in a place like Molokini, you got the right answer in part when you were told to ignore the DM and surface on your own. On the other hand, it should never get to that point if you are on a DM-led dive. The DM should know that you are getting on the low side long before it becomes a critical issue. If the DM doesn't ask, then make sure you tell him or her your situation clearly. If the DM asks and then seems to be ignoring the situation, then assume it is a misunderstanding and become insistent in your communication. Going back even further in time, you should not enter the water in such a situation without a clear understanding of the DM's protocols for asking for air and beginning the ascent.

If you have very clearly communicated a low on air situation and then recommunicated it if necessary, I cannot imagine a DM so incompetent as to continue to ignore you. In fact, I have never seen one ignore the original signal.

 

[MADiver]

The DM should know that you are getting on the low side long before it becomes a critical issue. If the DM doesn't ask, then make sure you tell him or her your situation clearly.

I signal it often - I always signal at 1500 and 1000 psi. The DM usually nods and continues the dive. My problem is that I usually hit 800 psi and still can't see the boat, and I'm just assuming that our DM is taking us toward it at that point. Every single dive so far, the boat came into view shortly after that. But in cases where I'm not sure if he's headed back to the boat (for example, when the dive site is not a sloping reef), I would be lying if I said I didn't start to get worried about whether the DM was taking us back to the boat or just continuing the dive. At that point I usually just chase down the DM, tap him on the shoulder and show the boat signal. The DM usually points me in the right direction and I'm on my merry way because we're close. I haven't had a guide misjudge my air consumption yet after signaling 1000 psi, but it's always on my mind during a dive and it's something I worry about.

How long should I wait before just heading to the surface with my buddy? Is 500 psi time to tap the guide on the shoulder and thumb it?

 

[Bubbletrubble]

How long should I wait before just heading to the surface with my buddy? Is 500 psi time to tap the guide on the shoulder and thumb it?

@MADiver: Excellent questions. The fact you are asking these questions means that it's high time to learn about gas management, the calculation of safe gas reserves, and how to be more assertive with your dive planning. Bob Bailey (NWGratefulDiver) has written a very nice essay on the topic. Check it out here.

Pay attention to your surroundings underwater and your comfort level will increase. Many of the DM-led dives I've been on have been out-and-back dives -- easily navigable by divers unfamiliar with the site. You won't have to ask the DM where the boat is...because you'll already know. The same can be said about taking charge of your own gas management. You and your buddy will simply be executing the plan that was discussed during the pre-dive phase. You won't have to wonder when to leave the DM-led group or when to ascend. You'll just know.

This means that when you inform the DM/guide of your remaining gas it's just an act of common courtesy so he knows where you went. The extent of your underwater communication with the DM would be: "I have XXXX psi remaining. My buddy and I are returning to the boat. Enjoy the rest of your dive with the group."

Hope this info helps...

 

[dumpsterDiver]

In each of my last two classes, I had students ask me to confirm what they had been told by their diving friends: there is no need to worry about things like tables and other things like that because the DM will make sure you have a safe dive.

I, of course, disabused them of that notion, but it is clearly a common one.

It might be good to explain to these people that a dive master gets paid far less then the garbage truck driver or possibly the maid who scrubbed the hotel toilet last night. Would you trust these other higher paid "professionals" with your life?

 

[Ken Kurtis]

Diving molokini crater comes to mind -- there were 12-15 boats coming and going throughout the dive (you could hear the all boat traffic from the bottom). Is it smart to head to the surface in relatively high traffic areas like that? This is something that I've had to consider before as I usually suck down air faster than the more experienced divers in my group.

I'm going to get oto your specific question in a moment. But first . . .

Part of all of this is contingency planning BEFORE you enter the water. What do I do if this happens? What do I do if that happens? And the answers to the this/that questions may change dive-to-dive or location-to-location. These may be things you work out on your own, with your buddy, or with the DM/guide.

Specifically to Molikini and the high-traffic . . . why do you think (I ask this rhetorically)that your only options are follow the DM and maybe run out of air, or surface on your own and maybe get run over by a boat?

Specifically at Molikini, you are likely diving very close to the bottom/sides of the dive site. Rather than make an ascent into open/unprotected water (where you might get run over) follow the bottom/side contour so that you're ascending right next to Molikini itself. The boats that might hit you are not going to be running that close to the island/volcano. Stay close, find your boat, signal them and then - when they're in pick-up position, you can safely swim on the surface to your boat.

And if they were anchored in the cove and you were on the backside, simply stay close to the island/volcano on the surface, swim the perimeter into the cove, and then back to the boat.

- Ken

 

[SoCalRich]

Great post.
I agree with teaching OOA procedures are nessary. And I also agree that maybe teaching that if you run out of air will most likely die. I often hook up with buddies that hardly ever check thier remaining gas supply. It always suprises me that so many divers don't cross check with thier buddie's gas supply.

 

[John C. Ratliff]

I'm going to get oto your specific question in a moment. But first . . .

Part of all of this is contingency planning BEFORE you enter the water. What do I do if this happens? What do I do if that happens? And the answers to the this/that questions may change dive-to-dive or location-to-location. These may be things you work out on your own, with your buddy, or with the DM/guide.

Specifically to Molikini and the high-traffic . . . why do you think (I ask this rhetorically)that your only options are follow the DM and maybe run out of air, or surface on your own and maybe get run over by a boat?

Specifically at Molikini, you are likely diving very close to the bottom/sides of the dive site. Rather than make an ascent into open/unprotected water (where you might get run over) follow the bottom/side contour so that you're ascending right next to Molikini itself. The boats that might hit you are not going to be running that close to the island/volcano. Stay close, find your boat, signal them and then - when they're in pick-up position, you can safely swim on the surface to your boat.

And if they were anchored in the cove and you were on the backside, simply stay close to the island/volcano on the surface, swim the perimeter into the cove, and then back to the boat.

- Ken
(emphasis added, jcr)

Ken, I use this technique when I dive the Clackamas River. I've tried using a dive flag, but in the current it causes all kinds of problems--a line for entangling, and I've actually had the float ripped off the flag by the current, allowing the whole business to drop to the bottom (we have some pretty good currents in places on this river). So I've simply been surfacing near the rocks, where any boat traffic would have to hit a rock to hit me. It doesn't need to be Molikini Crater to use this technique.

SeaRat

 

[John C. Ratliff]

Great post.
I agree with teaching OOA procedures are nessary. And I also agree that maybe teaching that if you run out of air will most likely die. I often hook up with buddies that hardly ever check thier remaining gas supply. It always suprises me that so many divers don't cross check with thier buddie's gas supply.

Okay, I've been reading on this thread for a week and still have not gotten through the whole thing. It's quite impressive. But I need to take some exception to how we are phrasing this problem. Why? Because, as a scuba diver who is not in an overhead environment (including being well within the NDL), you are never out-of-air (OOA)! Remember diving physics and the Universal Gas Law?

P1V1/T1 = P2V2/T2

This means at 33 feet I have the equivalent of two of my lungs full of air if I head for the surface. At 66 I have three, and at 99 feet I have the equivalent of 4 lungs full of air, even if the scuba has nothing in it. In addition, the same goes for the scuba unit itself. So when someone says they were "out-of-air," they really mean that they had no more air to draw from at that depth. But, they had plenty of air to make it to the surface.

When I was an instructor, NAUI had a requirement that before the class ended, the scuba student had to be able to swim 20 yards underwater with only a swim suit (and maybe goggles). I regularly breathhold swim 50 yards underwater with fins. Fifty yards is 150 feet, on one lungfull of air. How far can I swim on three lung fulls of air? Further, I will assure you.

In the US Naval School for Underwater Swimmers, we had to do a buoyant ascent from 30 or so feet. We would swim down to a bell, and then we'd duck out of it and hold onto the side while an instructor filled up our life vest with air. We would then do a "blow and go," exhaling as much air as we could easily do, then letting go and exhaling to the surface--we still exhaled a lot of air. We have what is called a "residual volume" of air in our lungs--air we cannot exhale. In that 30 feet it was enough that we continued exhaling through the ascent. The new information from the DAN site shows that this is no longer a good method of instruction, as there have been embolisms because of lung over-expansion from free ascent training in Europe. However, it was taught to a whole generation of Navy divers, and shows the concept well that we are not "out-of-air" at depth.

The notion that if we run out-of-air at depth we will die really ignores this basic fact of physics. What really we mean is that if we run out-of-air at depth, and stay at that depth or even need to go deeper, we will die. But there is plenty of air to make it to the surface. This is a very good reason for not pushing the no-decompression limits.

SeaRat

PS--SoCalRich, you might try using the spell-checker

 

[boulderjohn]

Great post.
. And I also agree that maybe teaching that if you run out of air will most likely die.

I simply can't express how much I disagree with this. Running out of air at depth is not good, but it is a problem that can be solved easily through a calm and reasoned response that is entirely within your training. Teaching people that if they run out of air they will most likely die has the opposite effect. It teaches them to panic and do the exact thing that will in fact kill them--sprint to the surface while holding their breath.

 

[flots am]

A lot of us new divers have no idea where the "exit" is.

Most new divers (including me) don't feel comfortable leaving a DM in the middle of a guided dive. Especially if it's a guided dive in a place you've never been, it's very easy to get completely lost during the tour and have no idea how to get back to the boat. I have almost no sense of direction underwater - all I've done is the simple compass swim during OW training, and that's the extent of my navigation training.

You really need to know how to end every dive without the DM. He may simply lose you. Or he may be a dumbass and continue on with his mob at a time when you're out of air and need to surface.

I don't mean to say that you should ditch the DM at any opportunity, only that I've seen my fair share that continued the dive even when some of the divers were very close to being OOA, and that you need to be able to end your own dive if necessary.

flots.