Seaduction Q&A - June 2010

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Q1) I am a PADI AOW with some 50 dives, use Nitrox, now Rebreather trained: I am a reasonably fit [gym 4-5/week to work out + Yoga/ Pilates], male, age 56yrs., never smoked, good health - diving mainly warm water.  I'm comfortable in the water, and feel my buoyancy is reasonably good.  My challenge is improving my breathing rate. Typically, for a 30m dive, a 15L cylinder at 220bar will give a bottom time of only about 40minutes.  I am improving gradually, and have recently progressed to shedding all but about 2 kg of my ballast weight.  On a Draegar Dolphin rebreather I have no problems with a 60-minute dive - but I would also like to improve my open circuit dive times. Can you suggest exercises/ strategies/ devices etc that can help with my air consumption further, please?

A1) Actually, your gas consumption is not bad for a diver of your experience.  The average advanced or technical diver in my classes will have a surface gas consumption rate of around 0.75 ft3 or 22 liters per minute with 75 to 100 logged dives and your gas consumption rate is slightly better at around 0,72 ft3 or 20 liters per minute.  However, you can obviously improve your gas consumption and a reasonable goal for excellent gas consumption is around 15 liters per minute or one-half of one cubic foot.  It sounds as though you are in good health and well conditioned so the predominant controlling factors for your gas consumption are probably going to be buoyancy control, trim, gear streamlining and swimming technique.  It sounds as though you are fairly happy with your buoyancy, but remember that your trim or attitude that you swim with in the water is every bit as important as your actual buoyancy.  The next time you dive, check your buoyancy while laying face down in the water in a proper swimming position at a depth of seven to ten meters, with minimal or no movement you should be able to hover motionless and stay in this swimming position for 1 to 2 minutes.  Achieving that degree of trim control will improve your gas consumption more than any other factor.

The other steps to take are streamlining your gear and your swimming technique.  Before you enter the water, be sure nothing dangles.  Octo and console hoses are the most common offending articles so tuck them away and insure that excess straps or accessories are also tucked safely away.  With a streamlined gear setup and good trim your swimming technique will naturally improve on its on but keep these steps in mind as well.  Keep your arms at your side or crossed tightly in front of you – swimming with your hands is ineffective and produces drag.  You also need to focus on slow long fin strokes, keeping your knees as straight as possible.  Slow, long strokes require less exertion and propel you further with every stroke.  Finally, the other thing that will help your buoyancy control and gas consumption is more experience.  I frequently tell my students that the first 50 dives are great for learning all the things that they need to correct and the next 2000 are good for correcting them.  The important thing in gaining experience is to evaluate yourself frequently and make adjustments.  Doing 50 dives is different from doing the same dive 50 times and the difference is self-evaluation.  Have patience – after 6000 plus dives I still perfect my skills on every dive!

Q2) I have looked at a number of regulators and noticed that the second stages come in a number of different styles with different features.  I think I understand the pros and cons of the so-called dive and pre-dive switches and the adjustment knobs that I am told adjust breath resistance.  However, I have also noticed that two or three companies have odd shaped regulators with side exhaust.  What are the pros and cons of these types of regulators, how common are they and do they cost more?

A2) Regulators of this style are more of a personal preference at this point in regulator evolution than a performance benefit and like all gear choices there are tradeoffs you have to consider.  With older, traditional style, second stages the regulators would have a tendency to free flow when swimming into a strong current and the side exhaust systems alleviated that problem.  So these styles were very prevalent in older product lines, however, most modern traditional regulators have solved this problem with covers or deflectors in front of the second stage diaphragms and the design is a bit less prevalent today as a result.  Probably the two biggest advantages of side exhaust regulators are that the regulator hose can be routed over either shoulder giving the diver more flexibility in how his gear is configured and when sharing gas it is impossible to insert the regulator in your mouth upside down since there is no upside down.  Most traditionally designed second stages are limited in these areas and if you attempt to use them upside down they have a tendency to leak a little water into every breath.  The most notable cons for the side exhaust regulators are that the purge buttons are located in a different position making them awkward for some divers when they first try them and most tend to be larger than designs that are more traditional.  However, a few familiarization dives with your equipment will address the purge issue and the size does not matter to many divers.  Some photographers and videographers prefer these 2nd stages because in most common swimming positions the regulators tend to deflect the exhaust bubbles away from the divers field of vision and do not interfere with framing shots or otherwise watching your subject.  These designs are available in both low performance and high performance regulators and they do come in different sizes and price ranges.  Several companies including Dacor, Mares, Oceanic and Poseidon make them.  So, if you prefer this style of reg, odds are you will be able to find one at a local retailer that meets both your needs and budget. 

Q3) I am pretty comfortable clearing my mask underwater, but I wear contacts and I often wonder what I would do if my mask was knocked completely off underwater. My instinct is to close my eyes to keep from losing my contacts, and with the mask off, it seems there are only two options: 1) open them and lose my contacts, hoping to find the mask (unlikely with bad eyesight) or 2) have my buddy retrieve the mask for me. Is there a recommended procedure for recovering a mask in this situation?

A3) First off, no matter how good your vision is on land, it will be horrible when you’re trying to see underwater without a mask. It is actually extremely rare for a diver to completely lose their mask underwater, but if you do, with or without contacts, it is unlikely that you will find it again unless you are not moving, it falls directly in front of you and it doesn’t get knocked around by current or surge. Closing your eyes is the best way to keep from losing your contacts, so you would need to have your buddy readily available to help you find the mask. If not, you’d probably need to do a controlled ascent without it. If you have dramatic concerns about the loss of your mask, take a tip from the technical divers: Because they are completely dependent on their mask to safely ascend and complete decompression stops at the end of a dive, many of them carry a spare mask in an accessory pocket on their BC or exposure suit.

Q4) During my open water dives, myself and two other divers surfaced with nose bleeds after our first day of diving and two of us suffered from muffled hearing for days after completing the dives.  Our instructor told us that nose bleeds were common place and the muffled hearing was just a result of having water in our ears.  Is this true or was he just covering up?

A4) Covering may be a bit strong; more likely, he was making the best of a bad situation.  Although nose bleeds are not terribly uncommon, they are certainly not good.  And, it is uncommon for a healthy diver who equalizes properly to surface with a nose bleed at the end of the dive.  What is common is for divers to have a sinus squeeze on descent and to either try to force equalization or ignore the pain until it goes away which results in swelling of the nasal tissues ultimately leading to the nose bleed you reference.  With regard to equalizing your ears.  “Water” cannot get into your middle air unless one of three things happens.  (1) You rupture your ear drum allowing sea water to rush in from outside.  (2) Water enters the middle ear by flowing up the Eustachian tube, a very, very difficult thing to accomplish.  (3) Fluid is squeezed from the tissues filling the space as the result of a severe squeeze.  This could even result in a rupture of the inner ear, the so called round window, which generally leads to some degree of hearing loss.  Creating a squeeze with enough intensity to fill your middle ear with fluid is an extremely bad idea and very dangerous for your hearing.  Remember to equalize as you leave the surface and every two to three feet for the first 30 feet of descent.  After that, you can equalize a little less frequently.  But, always pay attention to your body.  If you feel discomfort, you have already gone too far.  Ascend until all of the discomfort is gone, then equalize, and continue your descent.  In the event that you have muffled hearing after the dive, you can take a decongestant like Sudafed to speed the process of clearing the fluid.  However, it is really a bad idea to put yourself in this position and it can negatively impact your hearing.

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