June 25, 2010 – Dive on E2

I finally took a day off on Friday and was able to dive off of Phil’s rib.

On the way down, Kevin and I chatted about possible sites. But once we drove past Monastery, we knew that possibilities would abound. Calm flat seas meant that we had a high likelihood of rounding the point and diving further south.

At Pt. Lobos, Kevin and Phil discussed sites. Before long, we’re pushing off and heading towards E2.

Pt. Lobos - Looking to Sea
Looking to sea.

Hermissenda Crassicornis
Party of hermissenda crassicornis at 140′.

May 1 and 2 at Pt. Lobos

At least once a year, our friends from SoCal drive up and spend a weekend diving at Pt. Lobos. Not only are they are a great group to dive with, they usually bring fantastic weather. The swell model and top side conditions did not look promising, but once we got below 30′, Pt. Lobos opened up.

As the result, we had two unexpectedly beautiful days. Fun diving with our friends!

Lionfish in Bonaire

The first lionfish were reported in Bonaire in October 26, 2009. We are currently in Bonaire and have already spotted 3 lionfish, on three separate dive spots. Elissa spotted them at Angel City (73′) and 1000 steps (84′). I found one today at Tori’s Reef (60′).

lionfish at angel city, bonaire
Elissa spots this lion fish on April 5th at Angel City. He’s nicely tucked under an overhang of coral, and this shot was taken at an angle to expose him.

marking the lionfish in bonaire
Elissa marks the lionfish, and we continue on our dive at Angel City.


Video of Elissa marking a lionfish at 1000 Steps.

lionfish at Tori's Reef in bonaire
And here’s the third lionfish on our trip, marked and ready for pick-up.

Scuba 101 – Controlled ascents

One of the most important skills for new scuba diver to master is a controlled ascent. It is not uncommon for newer divers to feel okay at depth (>30′) but then feel unstable on ascents and in shallow waters – “I can hold my 20′ safety stop, but when I move shallower, I quickly find myself on the surface.” This is especially true for new cold water divers and new drysuit divers.

Fortunately, controlled ascents can be learned.

Scuba diver ascent
Picture by Toine Peeters

Proper Weighting
Carrying the appropriate amount of weight makes diving easier. Carrying too much weight adds instability into the scuba system, as more air is needed to compensate for the additional weight.

Obviously, it’s possible to manage the extra weight. But why do so when it’s unnecessary and makes diving more difficult?

Proper weighting is achieved when a diver can hold a 10′ stop without any air in the BC and with 500psi remaining in the tank. This insures that the diver can hold his last stop at the end of a dive.

Be a Proactive Diver
The most common statement I make while teaching a basic scuba course is “be a proactive diver. And not a reactive diver.”

Instead of waiting to react to buoyancy changes, it’s better to anticipate and proactively manage. On descents, this means adding air as one descends and thus stopping a few feet from the ocean bottom. An example of being reactive on descents is the diver that touches down on the ocean bottom and then adds air to lift him off the bottom and into a neutral state.

On ascents, being proactive means dumping gas from the BC when the diver ascends, before feeling a positive buoyancy effect. On an ascent from depths greater than 30′, this generally means dumping gas every 5′-10′ as appropriate. For ascents from 30′, this may mean dumping gas every 2′ or less, depending how you are managing your ascent rate and ascent strategy.

Getting in Front of the Buoyancy Curve
To be proactive on ascents, this means that the diver must get in front of the buoyancy curve.

Instead of adjusting once you get to the desired depth, adjust en route.

For the ascent, this means adjusting during the ascent, before you feel the buoyancy lifting you up. To do this, the diver uses the combination of lung and BC to manage the ascent.

Simplified, the steps would be as follows:

  1. Start neutral in the water column
  2. Inhale to start the ascent
  3. Dump gas
  4. Exhale back to normal lung volume
  5. You should now be neutral in the water column
  6. Repeat 1-5

Remember that the recommended ascent rate is 30′ per minute. That means from a typical safety stop of 20′, it should take the diver 40 seconds to reach the surface.

A proper ascent and bubble management would look something like below. The bubble is appropriately sized for the ascent, and not pulling the diver up and out of control.

Ascent Bubble curve

If the diver waits too long to manage his buoyancy, and gets behind the bubble curve, then the extra air in the BC will cause a rapid and potentially uncontrolled ascent.

The excess bubble (buoyancy) causes the diver to rise. This expands the bubble more and in turn causes the diver to rise faster and expand the bubble even more. I think that all of us in our diving career has felt the sensation of being carried away to the surface.

Ascent Bubble curve

Body Position
While I discuss body position in the scuba ascents and descent article, its worthwhile to revisit again. The horizontal trim position offers the diver stability while moving up and down the water column. This is because the horizontal trim position provides the largest vertical drag possible.

Please refer to the linked article above for a more detailed discussion of body position.

How to Lower Gas Consumption Rate

It is not uncommon that new scuba divers consume gas at a faster rate than more experienced divers. There are many factors for this and TSandM has a great write-up:

How fast you use your gas is determined by two things: How much CO2 you are generating per minute, and how efficiently you use the gas you breathe to accomplish gas exchange in the lungs.

To address the second idea first, I’m going to describe a little anatomy. Your respiratory system includes your mouth, larynx, trachea, large bronchi, small bronchioles and then the air sacs where gas exchange actually takes place. Until gas gets into the air sacs, it’s just passing through — it’s not delivering any oxygen, or taking away any CO2. If the volume of air you breathe with each breathe is only the volume of your larynx, trachea and bronchi, you’re moving a lot of air, but not exchanging any gas. That’s why shallow, rapid breathing runs through your tank quickly (and also leaves you feeling short of breath). It’s also why slow, deep breaths are routinely recommended by instructors.

Tension and anxiety tend to make people take quick, shallow breaths, which are inefficient. Relaxation tends to allow people to slow their breathing . . . but the funny thing is that slowing your breathing also tends to bring relaxation with it. That’s the essence of yoga breathing, or meditation.

Assuming your breathing PATTERN is an efficient one, then you have to look at your CO2 production, which is a result of metabolic activity in cells. You have a certain basal metabolic rate, below which you really can’t go. It’s actually HIGHER in fitter people than it is in the unfit, so you’d think that getting fit would make your gas consumption worse. But at the same time that your basal metabolic rate increases, the amount of muscle effort you need to accomplish a given amount of work goes DOWN, and that’s a much bigger influence. So fitness does pay off.

But efficiency pays off even better. Every motion you make underwater, you pay for with some gas used. Therefore, the less motion, the longer your gas lasts. You can reduce motion by becoming horizontal, so that all your kicking effort succeeds in propelling you forward. If you are tilted at a 45 degree angle to the bottom, each time you kick, you drive yourself upward. To compensate, you have to keep your buoyancy negative, so you will have an equal tendency to sink. At that point, you are expending energy for a net displacement of zero! Very inefficient, and a very common new diver error.

Use your fins, not your hands. Hands are great for swimming on the surface, without fins, because your feet aren’t very efficient propellers. But fins are, and that’s what you should be using underwater. Flailing wildly with the hands uses a lot of muscle effort and produces very little net propulsion, so people who swim with their hands tend to suck gas.

Master your buoyancy. Although the volume of gas going into your BC or drysuit is relatively small, if you are putting it in and letting it out and putting it back in and letting it back out . . . after a half hour, your BC has breathed a lot of your gas. To master buoyancy, you have to start with proper weighting, because being significantly overweighted will make you unstable in the water column, and result in a lot of yo-yoing that wastes BC gas and ALSO makes you breathe harder. So reducing your weight to the proper amount will, in the long run, make your gas last longer.

And finally, move slower! One of the major strategies of sea life is camouflage, so if you move quickly, you miss many animals you might otherwise find. Unless you have a specific purpose for rapid movement, like spearfishing (and spearfishermen are NEVER going to win any awards for low SAC rates!) slow swimming will result in a much more productive and interesting dive.

Finally, recognize that body size and muscle mass will have a detectable effect on gas consumption. My favorite dive buddy is 6′ tall and very strong. He’s an absolutely beautiful diver — quiet, relaxed, balanced and efficient in the water — but he will never equal my SAC rate, because I’m a little old lady. If you habitually dive with people who are much smaller than you are, then buying bigger tanks may be your best answer.

December 24, 2009 – Pt. Lobos

Elissa, Devin, and I met up with April, a visiting diver from Seattle. Fortunately for us, there was a mid week lull between two storm systems. As the result, we were greeted with calm seas and only moderate surge.

In the water, visibility was a clean 20′, and you could see outlines and shapes quite well at 30′ away.

The first dive, a friendly seal followed us all the way passed Lone Metridium. We separated at 70′, the seal resting at the bottom and us cruising along the western wall.

The second dive, April led us around Middle Reef. Some large cabazons, resting comfortably on rocky reefs.

Golden cabazon

camouflaged cabazon

crab

Hog looping – misinformation about the Hogarthian configuration

This week, BSAC’s “Technical Group Leader” sent a message to their technical instructor corp regarding BSAC’s position that the hogarthian configuration should not be taught.

While BSAC has prerogative to make any ruling on gear configuration or teaching methods and philosophy, it’s the misinformation about the Hogarthian gear configuration and the OOA procedure that’s unforgivable.

As the result, their decision has caused a justifiable stir on the Internet:

Below is the message originally sent to the BSAC technical instructors:

Dec 2009

“Hogarthian rigging” and “Primary take” when teaching “out of gas response” on BSAC courses

Dear BSAC Instructor,

The recent introduction of the BSAC Sports Mixed Gas course and the subsequent automatic upgrading of all Extended Range Diver Instructors with a mixed gas qualification to Sports Mixed Gas Instructor have highlighted a problem. This problem concerns the teaching of “Hogarthian rigging” and “Primary take” within BSAC courses in general and on BSAC Technical courses specifically. Instructors who have qualified via the instructor workshop or observed course routes will be familiar with the BSAC policy regarding these techniques. However, it transpires that many of you who have automatically upgraded from ERD Instructor or those of you who teach within the regular Diver Training Programme (OD, SD, DL & AD) may not. I am therefore taking the opportunity to remove any ambiguity by explaining the BSAC policy and the reasoning behind it.

Definition of terms:

“Primary Donate” is the technique of a donating the demand valve the donor is breathing from to an out of gas casualty, the donor then resorts to his/her alternative gas demand valve.

“Primary Take” is the technique were an out of gas casualty snatches/takes the donors regulator independent of any action by the donor, the donor then has to take up his/her secondary demand valve.

“Hogarthian Rigging” is the technique of routing a long (1.5 metre – 2 metre) primary regulator hose from the cylinder valve, under the right armpit, around the front of the body, around the back of the neck and culminating in the primary dmand valve being the one the diver is breathing from.

BSAC has conducted field trials and as a result have arrived at the conclusion that “Hogarthian rigging” and “Primary Take” are incompatible with techniques taught within BSAC training programmes, do not work efficiently without significant donor input in some circumstances and are incompatible with some equipment types.

BSAC is aware that these techniques are taught and promoted exclusively by one US technical diving agency and favoured by some technical diving instructors from other agencies which, whilst not necessarily promoting it do not proscribe it either. Therefore I would like to take the opportunity to clarify BSAC policy as it is important to ensure you all understand why BSAC has taken a firm position on these particular techniques.

Some instructors from other training agencies teach and promote “Primary take”. This is where the casualty is taught to take the primary demand valve from the donor’s mouth. Incident statistics have indicated that this has the potential to have serious and dangerous consequences. Most divers have not been conditioned to cope with such an event and there is an element of transfer of the problem from casualty to donor within this procedure. Fortunately current incident reports dicate that “Primary Take” is not a common response and most out of gas casualties have resorted to their conditioning by training to give the appropriate signal and accept donation. It can be readily seen however that “primary take” is completely incompatible with rebreathers. For all of these reasons BSAC does not support or allow this technique to be taught by BSAC instructors to BSAC members or on BSAC courses.

“Primary donate” clearly ensures that an out of gas casualty will receive a working demand valve that supplies a breathable gas and if confronted with an out of gas diver the donor will choose whether to donate his/her primary or secondary demand valve. As long as the secondary demand valve is readily and easily accessible and the donor is well practiced in dealing with it this is workable. However, it is worth noting that this is not the only method of ensuring this desirable result. An alternative gas demand valve prominently placed within the triangle of access can achieve this equally well and has the advantage that the donor does not need to remove his/her own regulator and thus possibly exacerbate the problem. This latter is also a system that recreational divers will be conditioned to and familiar with, a benefit in terms of reduced training requirement when moving to upgrade their diving skills but also a system they are familiar with if confronted with an emergency underwater.

BSAC fully approves and supports the use of long hoses (1.5 metres – 2.0metres) to allow freedom of movement between donor and casualty in any out of gas situation. However the question of whether the diver breathes from the long or short hose arises when a long hose is fitted. Divers using independent twin-sets have a dilemma in that they have to swap demand valves at intervals during a dive. Since with independent twin-sets both regulators are in effect primary regulators the only complete solution in this case is to have long hoses on both regulators such that which ever demand valve is donated there is a long hose to facilitate freedom of movement.

In the case of a twin-set fitted with an isolation manifold there is a primary and secondary regulator and many divers employ a long hose on one and a standard hose on the other. The decision as to whether to breathe from the long or standard length hose is defined by whether the diver chooses to adopt primary donate or alternative gas source. However, instructors and divers should consider that swapping demand valves at least once during the dive to prove bothregulators are in full working condition at depth is good practice. Having both regulators fitted with long hoses covers all bases and is worth consideration even with this configuration.

The field trials BSAC conducted with “Hogarthian rigging” revealed a number of issues. The primary and essential criteria when considering hose routing and stowage for the donation demand valve must always be ease and efficiency of deployment covering the widest possible range of deployment situations. Re-stowage is not and cannot be the defining criteria.

“Hogarthian rig” is favoured by some for the simple reason that it is by far the easiest method to restow, the donor can easily re-stow the hose without assistance. An instructor may demonstrate deployment and re-stow a number of times without difficulty. However, re-stowing is of little significance compared to efficiency of deployment. In a real out of gas emergency the out of gas casualty needs a quick, seamless and efficient deployment to facilitate a successful result. Having completed the donation and with the out of gas situation fully resolved it is unlikely that donation will be required again in the dive therefore the hose may then be re-stowed in any convenient way.

Deployment of a Hogarthian rigged demand valve can be problematic in some circumstances. The ideal situation is for both divers to be more or less horizontal and facing each other. In this situation the hose should deploy easily. Where both divers are vertical and facing each other in the water it will be necessary for the donor to rotate forward to facilitate deployment over the head. There is a possibility of dragging the donors mask strap off but this can be avoided by wearing the mask strap underneath the hood. If the casualty approaches from the left side of or from behind however, the donor must quickly rotate forward and to the left to allow deployment of the long hose. If the casualty approaches from below the donor then it is necessary for the donor to roll forwards to facilitate deployment. In these cases the donor has to take significant action to enable the technique to work and this becomes proportionately more of a problem with the level of stress and urgency being experienced by the casualty. BSAC does not advocate that Hogarthian rig cannot be made to work, it is merely that it is a
system that may require significant and speedy action from the donor to ensure it works, without such donor input there is significant potential for snag and pocedure failure.

In contrast an alternative gas demand valve placed within the triangle of access combined with a long hose, stowed carefully under elastic bungees, either on the side of a cylinder or under the elastic ties of a wing or indeed any other method of hose stowage that can be relied upon to deploy efficiently without any action needed by the donor to ensure rapid deployment, works effectively and efficiently in all circumstances and with all equipment types or configurations, including rebreathers. An added benefit of the above system is that all recreational divers will have been trained in the use of alternative gas source. Minimal retraining is required as the only new element is the long hose and method of stowage.

In summary, it is clearly desirable that consistent and uniform emergency response techniques are established. The advantages of adopting a system that is widely taught and understood world wide at recreational level therefore requires minimal reconditioning through training and works efficiently without donor input with all equipment types and configurations are self evident. Therefore on the basis of trials and evidence BSAC has opted to teach as a preferred technique:

1. Alternative demand valve stowed within the triangle of access
2. The donation of a demand valve when required
3. The configuration of a long hose/s stowed in elastic bungees such that it/they will deploy efficiently and seamlessly when required.

This preferred technique does not involve the use of “Hogarthian rigging” or “primary Take”. BSAC standards and policy require that these techniques cannot be taught by BSAC instructors to BSAC members or on BSAC courses. The various BSAC Course Instructor Manuals provide clear guidance on preferred techniques to be taught on BSAC courses.

I hope this has clarified the situation and given an understanding of the reasoning behind it.

Regards

Mike Rowley
NDC Technical Group Leader
techg.leader@bsac.com

Scuba 101 – Ascents and Descents

In many basic Open Water scuba courses, divers are taught vertical body position for ascents and descents. While there are some benefits to this technique, a horizontal body position is safer, more effective, and much easier to execute.

Body Position
The prone body position, preferred while diving, is also the preferred body position for ascents and descents.

Below is the prone/horizontal/skydiver body position:
scuba diver ascent in prone position

Below is the vertical body position that most divers use for ascents and descents:
scuba diver ascent in vertical postion

Drag
The horizontal diver position provides a significant drag in the vertical water column. The wider profile helps control buoyancy as well as slows the rates of ascents and descents.

scuba diver horizontal ascent drag

The vertical diver position provides less drag in the water column. As the result, it takes more effort to maintain position and rates of ascents and descents are faster.

scuba diver vertical ascent drag

The above illustrations are from the side profile. However, viewed from the top, the profile differences between the horizontal and vertical positions is even more dramatic.

For descents, it’s usually easiest to descend the first 2′-3′ in vertical position since it’s the most steamlined. Once the surface tension is broken and compression starts, then the diver switches to a horizontal position to help control the descent rate and allow for maximum mobility.

Platform
Because of the benefits of drag on the horizontal driver, this position offers the most stable platform. This stability is particularly useful if the diver becomes task loaded or needs to resolve an issue during descents, ascents, or safety stop.

Most diving issues occur during descents or ascents. Even with the appropriate equipment and bubble checks, the descent is when your gear is first being tested. In our local waters, descents are also a common time for buddy separation. During ascents, issues include OOAs and gas switching mishaps. In these situations, the diver needs to be able to maintain neutral buoyancy while resolving the issue. The horizontal position makes this much easier.

Field of View

During the descent, a horizontal position provides optimal field of view. Both positions allow for looking forward at your teammates, but the horizontal position provides a great birds eye view of the bottom.

The horizontal position does limit your ability to look above you. But teams should descend and ascend together, at the same rate.

scuba diving descent field of view

scuba diving descent field of view

During ascents, in areas where a total horizontal position ascent may be dangerous (e.g. ships overhead), then switching to a more vertical body position in the last few feet may prove helpful. However, the best ascent strategy is to ascend in teams and have your teammates watch overhead and behind you.

horzontal ascent as a team

Kicks
In addition to vertical drag benefits of the horizontal body position, the prone position allows quick access to all kicks. These could include the small kicks for positioning the diver with the team and the environment. It also includes large kicks to quickly reach a teammate if there is an issue.

A diver in the vertical position has less horizontal mobility. Kenn (Gombessa on ScubaBoard) notes the vertical position also reduces vertical mobility. In the horizontal position, tilting up or down offers quick adjustments. In the vertical position, moving up is easy but moving down requires a full inversion.

The biggest issue with the vertical position is the use of fins to maintain position in the water column. Not only does this require work (consuming more gas), kicking to control buoyancy is not a stable position. In order to maintain buoyancy or control, the vertical diver must manage the BC and kick a consistent cycle. Alternately, the horizontal diver simply uses the BC or breath control.

In addition, a diver kicking in vertical position has an impact on the environment. On descents, silt and sand can be kicked up by a vertical diver’s fin movement. It’s not uncommon to see great viz, until divers descend onto the ocean floor. Fortunately, this can be eliminated if divers descend in horizontal position with their fins parallel to the ocean floor.

vertical diver kicking silt

Rate of Descent and Ascent
While there’s generally prescribed rates of descent (slow enough to allow sufficient equalization) and ascent (30 ft/min), the overall goal is control.

Upon reading this article, Ben (ben_ca on ScubaBoard) made a good comment about the need to arrest your descent/ascent with relative ease. He recommends a range for beginning divers of 4-5 ft and advance divers of 1-2 ft.

Not only is this control helpful in managing ascent/descent related issues such as blocks, but it is useful in keeping buddy teams together and being available to help if required.

A good way to practice is to make predetermined stops on descents and ascents. For example, instead of descending immediately to the bottom, agree with your buddies that everyone will stop at 10′ and 20′. On ascents, safety stops can be done at 30′ for 1 minute, 20′ for 1 minute, and 10′ for 1 minute.

How to Descend

Below is high level descent strategy, the diver will need to adjust to local conditions.

  1. Signal descent, get confirmation
  2. Inhale
  3. Dump gas
  4. Exhale
  5. Confirm legs are not kicking
  6. Transition to horizontal position
  7. Look at buddy
  8. Look at environment
  9. Equalize
  10. Add gas to control descent speed
  11. Repeat 7-10 until hovering comfortably off the bottom

How to Ascend

Below is high level ascent strategy, the diver will need to adjust to local conditions.

  1. Start neutrally buoyant in horizontal trim
  2. Signal ascent, get confirmation
  3. Inhale to start ascent
  4. Look at buddy
  5. Look at environment
  6. Dump gas to control ascent speed
  7. Repeat 4-6 until the safety stop
  8. Conduct the appropriate safety stop(s)
  9. After safety stop(s), continue to slowly ascend until the surface