What would you do: Molested at 100' by an OOA Diver

[dumpsterDiver]

I know of two independent cases in Florida as well, a women I worked with and a guy I dove with.

---------- Post added June 16th, 2013 at 09:21 AM ----------

The whole premise of expecting people to be able to do a free ascent with no air from 100 feet is unrealistic for most recreational divers. It is far better to give them the skills to predict and monitor their own air so they don’t get in trouble.
I also think that we have ample evidence to know that running out of air kills people and new divers need to be educated that this is a very undesirable (and statistically dangerous) condition to find themselves in. This message should NOT be watered down by trying to instill some false sense of security that they can easily just swim up from 100 feet without breathing.
I used to practice ditch and don of the scuba unit in 60 feet when solo. I am sure I can still do it, so I am not coming from the perspective that a CESA is impossible in certain situations for certain people.

However, the idea that people can not plan a dive because they will get so stressed out during a dive that their air consumption rate will go completely through the roof and cause them to run out of air (without realizing it) is silly, but not near as silly as assuming that these SAME PEOPLE, in the SAME CONDITION are going to be able to perform a CESA from 100 feet in a safe manner.

 

[The Chairman]

SAC works on constant depth dives, and in pool like conditions

​

Perhaps you simply don't understand the role of SAC in a dive. At least, you're not demonstrating that you do in your posts. Don't worry, you're not the first to misunderstand how to use this tool and you certainly won't be the last.

A diver's got to know their limitations, so SACs are for planning, not for diving. If I am doing a dive that requires over a 100 cubic feet of gas at my current SAC, then I know that there is no possible way to do this safely on an AL80. I have the opportunity to either alter the dive or rethink how much gas I'm taking down. Jumping in the water without knowing if you have enough air to complete it is irresponsible and will lead to problems. It's as bad as diving without knowing your NDL.

However, once in the water, the SAC becomes mostly irrelevant, just like your NDL. I don't think I've met any diver who uses time to determine their air or time X depth to determine their NDL in the water. No, they use their SPG to track their gas supply just as they use their PDC to monitor their NDL. If they're smart, they'll check their buddy's supply at the same time they check theirs and they have already compared NDLs on the surface so they know which PDC to surface on. Frankly, I've never had anyone give me the finger for me asking about their air supply. In fact, I make sure we are all counting the same way before we splash and that they know that I'll be asking them from time to time. Safe diving is no accident.

 

[danvolker]

I think the way this happens in actual practice, is different from the SAC Computing concept....I think most recreational divers have a "sweet spot" in depth for a given size tank....with experience, they do some deeper dives, and quickly ( hopefully) realize that while the 80 was good for them on 60 to 80 foot dives, that if they want to do a 100 foot dive or a 120 foot dive, then they CAN NOT do it with an 80...so they see if the dive boat has 100 cu ft tanks, or 120's, etc....and after they have done "many" dives like this, most of these divers know how long they can expect to plan to stay down on these deeper dives....at least this is how I have seen it happen with most divers over time in Palm Beach.

These divers do a lot of monitoring of pressure gauges on the first several of the deep dives, until they know what to expect....

We have a whole range of reefs in the 60 foot depth range....then a whole series of reefs and wrecks around 85 to 90 feet deep....and then a bunch that are between 100 and 135. Divers that go out weekly, learn to pick the tank they need for the dive area THEY are going to.

 

[boulderjohn]

Rule of thirds, the end. Once divers want to do more than turn at 1/3, they might seek more info. But of they always dive rule of thirds (honestly), they'll never have to, no matter how challenging the dive is.

The rule of thirds is only one dive plan we teach related to gas management. Divers should look at the dive situation as they plan and determine which one applies to the dive. For recreational diving, I would say that it is the one least used. I know that I rarely use it when doing a typical recreational dive.

 

[beanojones]

There are different uses of the term by different people. Some confuse it with RMV, or Respiratory Minute Volume. To get past the individual terminology, you have a basic SAC rate that you know, and you adjust it for conditions, including varying depths, currents, etc. It's not that hard, and it really is pretty predictable.

What I say next may sound a bit snarky, but it is actually sincere. Your most recent posts indicate you really don't know a lot about what is taught when we teach gas management. Before you condemn the process, I strongly urge you to learn something about it.

If the depths and conditions are predictable, SAC rate planning might be predictable.

(And that is assuming one has a baseline breathing rate that does not vary wildly, which is simply an assumption I have learned is foolhardy. The same diver can tremendously increase their air usage by as much as a factor of five (depth independent).)

But, even if air usage from a given diver was not wildly variable, depths and conditions are completely varied for many recreational dives. We jump in daily and do a current check, because we have to, and that is mostly which direction the current is running. Once the current direction in known, then we plan our dive direction, but as to depth and how much current we are fighting, that is all once we are in the water. So workload and depth are completely unknown. The only fixed variable is the size of our tank.

And then add the fact that currents switch direction underwater, and for some dives we can drift, and others we cannot drift and sometimes we do not know if it is a drift or not, until we are well into the dive and the boat takes off.

Go ahead, tell me how gas planning would help these dives.

---------- Post added June 17th, 2013 at 01:23 AM ----------

I have the opportunity to either alter the dive or rethink how much gas I'm taking down. Jumping in the water without knowing if you have enough air to complete it is irresponsible and will lead to problems. It's as bad as diving without knowing your NDL.

Since many/most divers have very little control over the tank size or the site, on the fly is not only all they can do, but also all they need to do.

The idea that one can jump in without enough air to complete a dive is kind of backasswards way of looking at the tools that the diver has at hand. If it's their own boat, and they have ten size of tanks to choose from then they do. Most don't, and making the non border cases have to conform to the much rarer border cases is thinking backwards.

Just as I think worrying about what the NDL before a dive is mostly counterproductive. The computer and the SPG both work underwater for a reason. Planning for recreational dives is something that some like to do, but no one needs to do, other than the general outline and entry/exit considerations.

---------- Post added June 17th, 2013 at 01:25 AM ----------

Tee Hee Hee. Thanks for the laugh beano. That's a good one.

So, when I shore dive to 50' with an Al80 I should turn the dive at 2000psi, do my SS and probably end the dive with 1800psi. Get a lot of repeat buddy dives doing that?

I don't think you 'get' rule of thirds.

 

[TSandM]

Okay, beano, here's a real life example.

I dove today at one of Puget Sound's premiere shore diving sites. It's a VERY current-sensitive site, where I had had a bad experience of getting in at the wrong time on a prior dive, and encountering a strong down current we couldn't even scooter against, and had to crawl upslope, so I was more apprehensive than usual going into the dive. We KNEW we were diving off slack. We THOUGHT the exchange was small enough to get away with it.

We had scooters. Some of the dive would be scootering, and some would be swimming, and we didn't know how much current we would hit or where. We DID know the depth profile, because that's under our control (except in the occasions, like the dive cited, where it isn't). We pre-planned the dive with an agreed max depth of 80 feet, a dive time of 60 minutes, a probable average depth of 40 feet. A 60 foot dive with an average depth of 40 feet, at the high end of my usual SAC rate, would require 1490 psi out of the tank I was using, according to my calculator.

We did the dive. We scootered out, hit gradually increasing current which, in contrast to our expectations, was blowing us AWAY from the entry, instead of toward it. It was also blowing us down, and we blew the hard deck for the dive by two feet. Instead of having an easy drift home, as we had thought, we had to swim and scooter about halfway, at which time the current unexpectedly turned (it shouldn't have changed; it shouldn't have been going the way it was going to begin with, but given that it was going that way, it should have continued for the entirety of our dive). At that point we drifted. At the turn point, I was actually fairly anxious, because I didn't like the strength of the current and I wasn't sure if it was going to get better or worse, and I had a vivid memory of my prior bad experience. I knew I was breathing harder than usual at that point, and I monitored my gas to make sure my consumption, given our depth, wasn't way off base.

We headed back and finished our dive. 60 minutes, average depth about 45 feet, gas consumed . . . 1500 psi.

Now tell me that a dive where precise profile and current behavior isn't predictable prevents the use of gas planning?

 

[elmer fudd]

The rule of thirds originated with cave divers and it's meant to apply to overhead dives.

The idea is you will need as much gas to get out as you did to get in, plus enough to get your buddy out as well if something goes wrong. That's a bare minimum for cave or wreck divers, but for NDL dives of 100' or less with no overhead it's complete overkill and utterly unnecessary. Turning a shallow dive at 2400 just because you started at 3600 is absurd.

 

[The Chairman]

Just as I think worrying about what the NDL before a dive is mostly counterproductive.

Wow... again. Well, you are completely unreasonable in my eyes, and I've learned not to try to reason with unreasonable people. Have fun.

 

[supergaijin]

I believe Beano talks from a fairly limited personal experience in diving environments. Perhaps a broader understanding of diving might help with some of the concepts brought up in this thread and how they pertain to the 'world of diving'.
NDL's on the other hand are important no matter where you dive.

I would gather from Beano's posts that the clients there are making the very definition of 'trust me' dives with little or no pre-dive plan other than to follow the leader. Clients (more often than not) do not carry computers or follow tables leaving all deco information on the wrist of the leader. Gas consumption is up to the guide to verify and react appropriately. I may be completely off-base here but it sounds that way to me.

 

[ferris213]

I don't think you 'get' rule of thirds.

Can you explain it to us? 1/3 in. 1/3 out. 1/3 reserve...What's not to 'get'? The rule of thirds might work for tech or penetration dives, but isn't it excessively conservative for most rec dives (like the one DaleC describes?)