Keeping skills fresh

Diving like any other physical activity requires training and after the courses and certifications are under one's belt it is good practice to keep skills fresh ... Personally I tend to practice my skill circuit when I'm doing easy relaxing dives such as the familiar shores dives at Cirkewwa and Zurrieq as well as during long decompression on more demanding dives ... Repeating the skills outside the course framework and during normal dives keeps muscle memory tuned in.

A lot can go wrong when diving on a closed circuit rebreather, knowing how to handle issues that crop up before and during a dive will end the dive with a happy face. During TDI training it was drilled into my skull that before getting in the water I must run a series of tests, these test cover all the steps involved in the setup of the unit, so if per chance a step is incorrectly executed or omitted, when going through the pre dive checklist the error is caught and resolved.

There are three main tests;

Pressure Test

­    With the cylinders open, I run gas through all the buttons, counterlungs, ADV (Automatic Diluent Valve) and both the wing inflators (primary and secondary, since I'm using a double bladder wing)

 

The Electronics Test

­     The cylinders are opened, the unit is switched on and the software runs a number of checks;

o   the temp stick (Sofnoline duration),

o   batteries life, and

o   cell reliability (the cells check the partial pressure of Oxygen),

o   this test also gives the option of calibration which I opt to do every time before a dive, the unit calibrates the three cells and gives an average reading.

Positive & Negative Test

­     Closing the cylinders and the mouthpiece, the air is purged into the counterlungs which are further inflated to their maximum capacity orally through the mouthpiece, this tests the counterlungs and connections under positive pressure.
    After a few moments if the pressure remains unchanged the air is vented from the over pressure relief valve &/ the mouthpiece and any air left inside the lungs is sucked out orally, at the same time squeezing the breathing hoses, this tests the counterlungs and connections under negative pressure.

­     If either of these tests fail, all the connections are checked to make sure they are finger tight closed properly.

Once the unit passes all the tests then it is good to dive.

What if I encounter a problem during the dive?

During any type of dive, recreational or technical I always carry enough bailout gas that will enable me to abort and end my dive safely, should something go amiss on the Rebreather.  On recreational dives I normally carry two cylinders one with 21% - Air and the second with a Nitrox Mix, usually 60% or 70%, on technical and more demanding dives I carry a third tank with a Trimix mix suitable for the bottom depth of that particular dive.

There are a number of skills, which once mastered can get any diver through different situations.  Similar to knowing how to remove and replace a mask underwater gets a diver through, partially, fully flooded mask or lost mask.

Mouthpiece removal/replace

Knowing how to safely and comfortably remove a rebreather mouthpiece is a key skill when diving on closed circuit. For those that are not familiar with rebreathers, the mouthpiece must be closed before being removed from the divers’ mouth.  Failing to close the mouthpiece properly will cause water to enter the unit and flood and damage the electronics.  Once the mouthpiece is closed and removed it naturally floats above the divers’ head, since it is positively buoyant.

One starts to breath through the bailout gas, open circuit regulator.  Retrieving the loop and returning it to the mouth before opening it is very important for the same reasons mentioned earlier.  Once the diver has the loop safely in his/her mouth then it is safe to exhale, any water lurking in the mouthpiece will be purged and the diver can start breathing normally.

Gurgling sound in the breathing loop

Sometimes condensation or a little water in the mouth piece can create an annoying gurgling sound, which can be easily cleared, this is done by closing the mouthpiece, extending the loop above the head, stretching the arms as much as possible and tilting slightly to the right, any water lurking in the loop will be safely drained into the counter lung.

Practicing this skill when there is no water in the loop keeps it fresh for when diving at depth and the skill needs to be performed quickly and effectively.

Bailing out at depth

     

Whilst diving the diver switches to the off board gas, whilst breathing from the bailout tank that way one can identify and resolve most situations that arise. The procedure; Close the mouthpiece and remove it from the  mouth, open the bailout gas suitable for the diving depth, trimix, air or rich nitrox, purge the regulator and breath ... Check the cell readings on the Vision handset and if all is in order, prepare to go back to breathing the CCR ... ahhhh silence at last.

Should the situation not be resolved, switching the rebreather to open circuit, immediately changes the setpoint from high (1.3) to low (0.7), diver should remain on open circuit bailout gas, switch the back up computer to open circuit, check decompression status and begin a safe ascent to abort the dive.

Closing the on board cylinders

Being able to reach the on board cylinders is also a key skill, which is not easy to master especially when carrying one or more bailout tanks.  However with patience and practice it becomes second nature to reach behind and feel for the cylinder knobs and turning them closed.

The manufactures' advice is that the Oxygen cylinder valve is only open by one or two turns max to enable quick closure in case of emergency.

High Oxygen also known as the “Oh Shit !!!” Moment

Several reasons why there could be a High Oxygen warning, these include; an Oxygen Spike, which happens when the descent is too fast, slowing down the descent should resolve the issue.  Another reason could be that the partial pressure of Oxygen (ppO2) is rising quickly, if this happens, the steps to follow are;

Switch to bail out, close the oxygen cylinder, check that the pressure gauge goes to Zero, flush the loop with diluent (this reduced the existing ppO2 in the loop), by pressing  the diluent button and at the same time, pull the overpressure dump valve cord (this is done to avoid a rapid ascent to the surface). Open the O2 Cylinder slowly, check the readings on the handset and check the pressure on the pressure gauge, return to breathing from the loop and monitor the readings on the handset.

I must admit it is an unpleasant experience to hear the buzzer going and see the heads up display flash bright red, the moment I look at the handset and notice a high oxygen warning I’m never happy, but keeping the “Oh Shit” drill fresh gives me confidence that I can perform the skill and solve the problem safely.

In the four years I have been diving Closed Circuit I have encountered very few problems which couldn’t be solved – I am very happy diving my AP Rebreather and if I had to recommend Closed Circuit Rebreather diving to my buddies I would say;

1. Make sure you follow instructions, checklists and manufacturers' warnings.

2. Do not sign up for Rebreather Diving if you’re planning on cutting corners and saving money on batteries, Sofnoline & cells – you’re cutting corners with your life!

3. Take care of the unit, it will take care of you.  Maintain the Rebreather, rinse the unit and lungs after every dive, service it as per manufacturers' instructions & replace consumables as and when necessary.  Send the electronics for periodic servicing to the manufacturer.

4. As in Open Circuit Diving - Know your equipment, set it up diligently and always use a check lists.

Gone diving

The preparation for a dive is nearly as exciting as the actual dive …. I often say this statement and I believe it.

Usually I receive notification of an organised dive in the start of the week, for the dive to take place over the following weekend.  This gives me something to look forward to during my work week and gives me ample time to plan and get my gear together for another underwater adventure!

Since Zeus is behaving very well lately I try not to miss out on any dives unless I have more important commitments planned, hmmm what commitments?  I immediately get on with making arrangements with one of my dive buddies who either dive open or closed circuit.  We discuss dive plans and what gases we will be using for the specific dive. Following that I arrange to have my tanks blended or topped up as necessary, I analyse and label them.  If I’m diving beyond the recreational limits, deeper than 45 meters then I will usually go for a 10/50 Trimix as my diluent gas, 60% Nitrox & Air as a bailouts.  For more demanding dives beyond 75 meters, I will carry a third bailout tank with a suitable Trimix for that depth, which will be used in an emergency until I can switch to air and Nitrox at shallower depths.

Following my training and out of habit I share my dive plan with my buddy/s to make sure we are all on the same page, planned dive time, max depth, available gases, plus a contingency plan, 5 minutes longer 5 meters deeper.  This is usually done over email or Facebook.

Come Friday, I get my rebreather put together, the unit would have spent a week dismantled and airing out.  I follow my check list to a tee; checking if I need to change the Sofnolime, I check the units electronics (batteries, cells and other hardware/software checks), I make sure I have the diluent I’m using set up on the Vision Electronics. Finishing off with a positive and negative check to make sure all connections are sealed tight.  I leave the unit on negative while I turn my attention to the other kit.

I pack my semi dry, booties, socks, gloves and a clean towel.  Then I turn to my bucket of other accessories; check my spare mask, knife, slate & depth timer (with plans written and taped up), reel & smb, torch, fins, regulators for bailout tanks, weights, back up dive computer, my Liquivision XEO (with the dive gas selected and batteries checked) and bezel.   I fill a bottle of water with some soapy water for easy donning my semi, that way I don’t have to struggle, the suit slips on like a glove.  I put a couple of bottles of drinking water in the freezer, and pack my wind breaker, towel and a spare swim costume in my dry bag. Last but not least I check that the electronics spares box (batteries & cells) and tool box are all in order.

The unit is purged from negative and if the dive is happening Saturday I pack everything in the car (rebreather, wet box with suit etc, accessories bucket, dry bag, tool box, analyser (just in case, I always re-analyse the cylinders before a dive), 2 x 3 litre tanks (rebreather) and 2 or 3 x 7 litre bailout cylinders), everything fits – I have a system!  The car spends the night safely locked up in the garage in anticipation of an early morning departure.

Come morning, I have a cereal bar washed down with some fresh coffee, if I dare, since if the sea is a little choppy I know I will be turning fifty shades of green by the time we reach our location!  If thats the case I have nothing except a glass of water.  Take the bottles from the freezer, maybe pick up a snack from the cupboard for later and off I go.  For the deeper wreck dives the boat usually leaves from the South of the island so that’s around 40 minute drive at 07:00 on a weekend, it’s rare to come across traffic at that hour and it’s a pleasant and relaxing drive with the right music.

Once on site, I greet the team - if there are any other early risers and start unloading the car, rebreather, tanks, bucket, suit, water, dry bag all check!  Once the tanks are installed on the rebreather and the bailout tanks have the regulators installed, I run through the rebreather check list one more time, better safe than sorry then I’m good to go – 20 or 30 minutes before the boat is scheduled to pick us up I get into my semi dry.  By this time the sun is up and it’s hot, but getting into a wetsuit which is soaked in soapy water isn’t all bad since I find it keeps my body temperature low.

Before a dive there is the usual banter from the other divers, there is always someone with a new piece of equipment to show and tell.  At the moment everyone is flashing new Shearwater Petrels …. Nice piece of kit I must admit.  Once the boat berths and the skipper greets us all and gives us our places in buddy pairs, we start to haul all the gear on board in an organised fashion (not).  But eventually we all get there and everything is in order.

We get our briefing from the skipper; only to jump in as buddy teams, don’t tug at the shot rope, once surfaced, signal and wait by the shot rope buoy for pick up, and finally the bit I like most, wait for the life ring and clip your stages before being towed back to the boat …. Ah to rid myself of the extra weight before boarding the boat, bliss!

Now for the all-important part …. The actual dive.

Diver teams start donning their equipment and getting ready to jump in after the skipper finds the dive site or wreck and sets up the shot and deco ropes.  We jump off in pairs on the skippers’ signal, swim to the marker buoy, make sure everything is ok and we are comfortable, signal descent, acknowledge with an OK and deflate wings to start the descent.

Once beneath the waves I have two concerns, is the shot leading to the wreck? and is my rebreather performing; are the cells reading ok?  I keep an eye on my buddy whilst we descend to 60 or 70 meter.  This takes some time (3/4 minutes) especially if there is a current.  Once we reach the wreck, I take note of the location of the shot. After that it’s all about exploration; if this is my first visit I try to take it all in, if I’ve already been to the site, I usually try to head to parts of the wreck that I haven’t fully explored.  It’s amazing no matter how many dives I make on the same wrecks, I always see something new, something I missed on previous occasions or something that another diver uncovered or moved on the site.  The wrecks that are found in the southern waters of the island are either World War I or II, they vary in size but for sure they never disappoint!

Lately I’ve been working on improving my trim, while swimming around I try to keep my trim in mind, challenging myself to penetrate tighter spaces than I would normally consider and minimally disturbing the environment/bottom.

Time is always flying when you’re having fun!  Soon it’s the 15 or 20 minute mark and we need to signal to return to the shot unless we are further away in that case we would be on our way earlier than the planned ascent time.  Once at the shot we start the long decompression to the surface.  Deco is usually around 30/40 minutes before we are bobbing at the surface waiting to be picked up.  During the ascent I keep close enough to the shot that I can grab the rope in case of emergency, if there is a current then I ring my thumb and fore finger, during this part of the dive the rebreather is trying to keep to the set point of 1.3, while I’m ascending to shallower depths and the existing content in the counterlungs is expanding rapidly.  I remain focused on reading the cells, monitoring my partial pressure and exhaling occasionally to keep a minimum loop volume and the current deco stop limits and keeping eye contact with my buddy. When we reach our 9 meter mark, we usually swim off to one of the shorter ropes on the deco station, where deco is continued.  As buddy pairs or team members we like to stay close at this stage, since anything can happen during deco as much as while performing the dive at the bottom.

Once the decompression is complete, and so is my buddy’s we remove the back clips of our bailout cylinders, signal to surface, acknowledge and surface.  At the surface we inflate our wings and signal the skipper that we are OK.  Most recently I have adopted a different method to feed my wing, I am using the Air bailout tank, so while the boat is approaching I close the tank, purge the regulator and unclip the LPI from my wing.  I have tried on several occasions to undo the LPI with an open cylinder but it’s a skill I have yet to master! Once the skipper throws in the life ring both tanks are ready to be clipped on, as soon as both divers have ridded themselves of the cylinders, the skipper pulls us back towards the boat.

Back on the boat, I turn off my unit, unclip all the clips and tie it securely it to the bungees, I collect my fins which would have been removed earlier by the skipper and stuff everything in my bucket.  I’m usually bursting to pee …. this would be a good time to get back in the water and relieve myself. AS buddies we all give a helping hand to help the other divers back to the boat, thus relieving the skipper from having to tow each diver/team back.  After the roll call is complete we head back to shore.  Everyone is talking over everyone else, “did you see the grouper?” “did you see the torpedo?” “what about the huge moray eel hidden in the loo?”

Most of the time everything is bigger and larger than reality …. But it’s not our fault, everything appears large underwater, it’s a fact!

Back to shore, all the divers unload their gear, and bring their cars around to load and head off for a cold Cisk or Shandy.

Until the next one....