Diving students can be overwhelmed by the number of complex motor skills that they need to learn and develop - all at the same time- as they progress through the Open Water course. It takes time and practice to get the hang of it. The Open Water course manual and DVD only get you started. One of my roles as your dive instructor and mentor is to help you develop a higher level of skill right from the start of your diving life, by giving you more information, so that you don’t have to think through the motor skill mechanics of diving all by yourself.
One way to learn is to break down a complex series of actions into their individual components, then think it through and visualize yourself performing each discrete step. As you practice in your mind, gradually increase your speed until you achieve a fluid motion.
There are four discrete steps to take to clear water out of a flooded mask. With practice, these will all flow together.
Look upwards to pool the water at the bottom of the mask.
Press your fingers against the top rim of the mask to hold the seal against your forehead.
Inhale deeply through your regulator.
Exhale with gentle force out your nose...snort!
Repeat as many times as necessary.
To visualize this process, imagine that you're blowing your nose into a kleenex tissue. When you blow your nose, you position your fingers to press against your cheek bones. So when clearing a mask, imagine you're blowing your nose…. but press your fingers against your eyebrows.
What happens when you perform this skill is that when you exhale out your nose, the increased air pressure inside the mask will break the seal against your skin just above your mouth and the air pressure will force the water out the bottom of the mask where the seal has been broken. Too easy!
Your nose has only two functions inside a scuba mask: to equalize mask pressure and to blow out any water that has leaked in. Both involve exhalation only. Your nose serves no other purposes, so you need to practice to become a mouth-only breather. Many new divers have some difficulty adapting to this, so I recommend that they practice mouth-breathing at home. Plug or pinch your nose, relax and breathe deeply into your diaphragm. Exhale fully. Wait for the breathing reflex to kick in, then inhale fully once again. Do this exercise for a couple of minutes every day.
Buoyancy Control -keeping forces in balance by managing three balloons
Buoyancy control is possibly the most critical dive skill. It's all about developing a situational awareness and skill to control your body position and movement in three-dimensional liquid space, so that you can multitask.
Since your total weight (body weight + gear weight) remains basically constant during a dive (minus the weight of the tank air consumed), you manage your buoyancy by adjusting the volume of air contained in three air vessels, or balloons: The BCD, which contains an air bladder, your drysuit, which is a sealed air vessel, and your lungs (breath control).
A diver must effectively manage the relative positions and volumes of these three separate air bubbles to remain stable and neutrally buoyant at any depth during a dive. And efficient propulsion/maneuvering skills must be developed, to keep opposing forces in balance - the force that makes you sink and the force that makes you float.
Most new divers have some challenges finding and maintaining their balance, achieving neutral buoyancy and staying neutral throughout a dive, especially when trying to hover in place motionless. It’s common for new divers to get caught up and struggle in a zigzag pattern where they can't control their balance, body position, and depth for any length of time. Zigzagging up and down can occur for any of several reasons such as poor situational awareness, slow reaction time, overcompensation for a small change in buoyancy, improper weighting, poor trim and hydrodynamics, inefficient finning and poor breath control.
Poor buoyancy control magnifies the risks of an accident and injury. Rapid ascents can result in decompression sickness, lung over expansion injuries, an arterial gas embolism, blackout and drowning. Uncontrolled or rapid descents can result in serious ear injuries if the diver isn’t able to equalize fast enough.
To understand what is happening to a diver with buoyancy control problems, visualize a tug of war rope, with forces trying to make you float pulling you up and forces trying to make you sink pulling you down.
Visualize that you’re all geared up and in the water, floating on the surface but not swimming. Forces to make you sink include your body weight plus the weight of the gear you’re wearing. The force trying to make you float is the volume of water that you’re displacing. The more water displaced, the more buoyant you will become. If your BCD is full of air and there is air in your drysuit, you’re displacing the maximum volume of water and will float high on the surface. If you now purge excess air from the drysuit, exhaust air from the BCD and exhale to empty your lungs, you’ll displace much less water, so the weight of your body and equipment will cause you to sink.
For most drysuit divers around Vancouver, it will take 20-25% of their body weight in lead weights in order to sink and be properly weighted.
The BCD contains an air bladder - a big balloon - which is your main tool for establishing and maintaining the balance between the forces to sink and to float. Its’ low-pressure inflator/deflator hose is the equivalent of a cars’ steering wheel. You need to be holding onto it in your left hand at all times (except when checking your gauges) and making lots of small adjustments just like you would driving your car on city streets. This is how to hold the low pressure inflator: thumb on the inflation button, index finger on the exhaust valve, and your three other fingers grasping the module. With this grip, you will always be in a position to inflate the BCD orally if necessary because the air intake/exhaust hose is facing your mouth.
As you dive deeper, air in the BCD will be compressed by the increasing pressure, so you need to add air to maintain neutral buoyancy and prevent sinking. Conversely, as you move up from deeper water to shallower water, pressure decreases so the air in your BCD will expand. You will need to exhaust air from the BCD to maintain neutral buoyancy and prevent an out-of-control ascent.
The drysuit is connected to the tank by a low-pressure hose on the regulator. You control the volume of air inside the drysuit with an inflator button and an exhaust valve, like with the BCD. To maintain neutral buoyancy and prevent a suit-squeeze, add air when you're descending and exhaust air when ascending. Use your right hand to deploy both the inflator and deflator buttons.
If you're wearing a drysuit and you let your arms go weak/limp and fill up with air, you'll create bulging balloons of air at your shoulders, with little air around your lower body. This will throw you off-balance, and will often cause you to become positively buoyant. And it can cause the air bubble to escape through your neck or wrist seals, which will let water in to the drysuit. Keep your elbows down and arms tucked in close to your body!
Drysuit divers will purge excess air and set the exhaust valve to the closed position to get ready for a vertical descent, then add air to the drysuit during the descent to prevent a suit squeeze, and open up the valve when they get into a horizontal position at depth. Once the exhaust valve is opened, the drysuit will automatically exhaust excess air. This means that anytime the diver feels positively buoyant, all they have to do is rotate/roll their left shoulder upward for a couple of seconds to let the excess air exhaust itself, then rotate back to down to level their shoulders.
Propulsion and maneuvering techniques
All your underwater propulsion comes from the action of finning. It's a waste of energy and tank air to use your arms for propulsion. And multitasking is impossible if you're doing the breaststroke underwater. Proper, effective and efficient finning techniques involve converting power into thrust…it takes time and practice to develop this skill complex motor skill. At first, you’ll need to consciously think about and manage your finning technique. After a while, it’ll become second nature.
The two main finning techniques are the flutter kickand the frog kick, which are used primarily for straight-ahead forward propulsion. The basic Open Water course introduces students only to the flutter kick, ignoring the frog kick and other, more advanced finning and maneuvering skills that you should be aware of and consciously practice as you develop your skills.
For more information on finning techniques, see this Wikipedia entry, which includes some links to demonstration videos.
Flutter kick mechanics
Efficient finning involves moving your legs and feet like an oar in a repetitive cycle to deploy the blades of your fins as paddles. These paddles push against water to generate the forward thrust that moves you through the dense water medium. Your hips, knees and ankles operate as hinges on a long oar that extends from your hips to the blade of your fins. Your various upper and lower leg muscles manipulate and power these paddles through the water.
The kick cycle begins with one leg bent at the knee (1) and the other leg fully extended (3), as shown in the pic and graphic below. The left leg is extended and nearing the end of the down stroke, and the right leg is being bent at the knee on the upstroke.
For the next cycle the diver should plantar flex the right foot (2) and flatten the left foot (4). Toes are pointed to position the fin optimally for the down-stroke, and the foot is flattened to minimize fin drag on the up-stroke.
Next, straighten the the right leg in a sweeping motion (3), which will power the fin downward in an arc; bend the left knee back up to the starting position.
In the example above, almost all of the leg movement is from below the knees, so it’s a finning technique best used when you’re moving along slowly. It doesn’t generate a lot of thrust.
For more power and thrust, the upper leg muscles -hip, thigh and hamstring- are used. Legs stay straight below the knees. The knee itself is stiff but not locked. Power is generated from the upper leg muscles and hips on the down stroke.
Using different muscle groups
When swimming at a moderate speed using the flutter kick, power comes from the hips and thighs. Keep your knees flexible, and ankles loose to flex on the linear plane, but stiff laterally. This is because if weak ankles allow the fin to wobble or cut diagonally though the water, you’re in effect kicking with a fin that’s no wider than your foot. Propulsion is best when you follow through and not cut the fin-kick cycle short. Glide between fin kicks, until your forward movement loses momentum. Kick, kick and glide, kick, kick and glide. This will keep your heart rate down, improve your air consumption, and give your legs some resting time.
For slower flutter kick speeds, for example when you’re scoping out a small area, thrust comes mainly from your calf muscles, or below your knees, because you don’t need the full energy that comes from your hips and thighs. The thrust power comes from the action of straightening your leg…the down stroke. While one leg is extending and thrusting downward, the other leg is bending upward. The frog kick is a good alternative technique when slow moving, especially if a flutter kick over a sandy bottom would raise clouds of silt.
Alternating occasionally between the flutter and frog kicks while swimming along will allow you to work different muscle groups, spread fatigue across these different muscle groups, and reduce the risk of cramps.
When swimming into a current, use the flutter kick with legs straight and thrusting from the hips and a shortened kick cycle. Currents will reduce or completely offset the forward momentum between kicks. There’s no gliding, so the diver has to kick constantly to make forward progress. Pro tip: if swimming close to a rocky bottom, use your arms to pull yourself along, so that you can rest your legs and get your heart rate down.
When ascending vertically straight up, like at the end of a dive, keep your legs straight, your toes pointed downward and your ankles loose linearly but stiff laterally, thrusting from the hips.
Many new divers become fatigued by water resistance against their fins as they swim around. To avoid thigh muscle burn, these divers swim like they’re riding a bicycle or climbing a ladder. This involves bending the knee up towards the torso, then straightening it. It kinda looks like a flutter kick, but generates almost no forward thrust. In fact, the upstroke action of lifting the knee serves to push water backwards, which slows you down. And the down stroke results in pushing the fin blade through the water rather than sweeping it, which generates little thrust.
Most 40 minute dives cover a distance of 500m or less. Some of this bottom time will be spent hovering in one spot, some time swimming slowly and some time swimming faster between points of interest. Different finning techniques can be used for each situation.
It’s a waste of energy to use your arms for propulsion, so the proper swimming position is with both arms folded across your torso to minimize drag and support your balance. Arm movements are really only useful for close-in maneuvers and sharp turns.
To optimize propulsion potential as you’re swimming along, you need to align your body hydrodynamically to the direction of travel, to minimize water resistance/drag. This means that your body should have a 0-30 degree upward angle from a level horizontal position, with your shoulders higher than your knees, so that you can look forward without craning your neck. Keep your back moderately stiff/arched. Knees are half bent, so your feet and fins are higher than your knees. Don’t let your feet drag you down into a steep angle…that’s bad hydrodynamically and will force you to swim harder alongside your more-hydrodynamic dive buddy.
And don’t let your knees and fins get higher than your shoulders, because air in the drysuit will migrate to your lower legs and will force your body into an inverted position.
Situational awareness when inflating or deflating the BCD or drysuit: estimating volume changes by proxy (sound)
It's not possible to estimate the physical volume of air that's being pumped into or exhausted from the BCD or drysuit at any given moment during a dive. You keep track of this net volume by proxy: by estimating the number of seconds that you've pressed the inflator button or exhaust button. The only way to do this is by listening to the hissing sound that's made by the inflator valve, and the bubbling sound made when air is exhausted.
It’s important to add or exhaust air in small increments - one second bursts - to avoid overcompensating and flinging yourself in the opposite direction.
If you're adding air to the BCD to offset negative buoyancy, do it in one-second increments and listen to the hissing sound to estimate this duration. Use your inner voice to count "one thousand and one". Wait a few seconds to determine how much this additional air has changed your buoyancy. If you're still negative, press the inflator and count "one thousand and two".
If you need to exhaust air, lift your left arm (holding the low pressure inflator and exhaust hoses) as high as you can as you press the exhaust button, to make sure that air is efficiently exhausted from the BCD. Watch the bubbles as you exhaust the air, to see how much you have dumped. And listen to the bubbling sound this air makes as it exits the BCD, to estimate the number of seconds of air that you've exhausted.
Similarly, add air to a drysuit in one-second increments. Exhaust air from the drysuit by lifting your left shoulder, raising your arm and bending the arm down at the elbow. The bent arm will prevent air from rising all the way up your arm, which would risk blowing through the wrist seal.
While some new divers tend to positive buoyancy, others tend to keep sinking. Resist the temptation to swish your arms when you’re sinking. It’s too little compensation and a waste of energy. Instead, squeeze the inflator button for one second, wait a moment to see if you've added enough air, and if you need to add more then add air in one-second bursts.
Body positioning, centre of gravity, and centre of buoyancy
Most body weight and lead weight are located around a diver's mid-section, with lead weights positioned close to the belly. This is the diver's centre of gravity (your core), and it acts like ballast. The diver's centre of buoyancy is located above the centre of gravity, around the lungs and the BCD's air bladder.
In general, the greater the vertical distance between your centre of gravity and your centre of buoyancy, the more stable you will be and the easier it will be to stay balanced. This is one of the reasons why wing-style BCD’s are generally preferred over jacket style BCD’s by serious divers. In a wing style, the air bladder is totally behind you, while in a jacket style, the air is distributed mostly around your sides, closer to the centre of gravity.
When a diver is swimming along, it's helpful to use a visual "spotting" technique to support proper body positioning and to provide a visual destination to swim towards. This involves looking ahead in your direction of travel, seeking to visually spot and fix something in the distance that you can swim towards. This technique helps to maintain situational awareness of your depth, speed of travel, visibility conditions, navigation, etc.
Breath control is a critical dive skill that can only be mastered over time. While the course manual suggests that you should breathe normally underwater, it’s a different kind of normal than the way we breathe on the surface. The skill involves consciously managing your respiration to oxygenate your body efficiently, and effectively .
The basic breathing pattern while swimming along involves saturating your lungs effectively with oxygen, so you should :
1. Inhale slowly and deeply for 3 to 4 seconds, fill your lungs
2. Hold the air in your lungs a for couple of seconds, to maximize oxygen absorption
3. Exhale slowly and fully for 3 to 4 seconds, empty your lungs
4. Wait for the breathing reflex to kick in…
The breathing reflex is controlled unconsciously by the body’s need to keep the partial pressures of oxygen and carbon dioxide in arterial blood at a constant level. Your body will tell you when it’s time to inhale. Don’t over-breathe, it’s inefficient management of your air supply.
The basic breathing pattern can be interrupted at any time when necessary to perform maneuvers.
Overexertion will overwhelm a diver’s ability to maintain the basic breathing pattern. This can give a diver the feeling that they’re not getting enough air from the regulator…oxygen starvation. If this happens, then the diver must slow down, or stop and rest to get the heart rate and breathing back under control.
Incidentally, good breath control skills will enable you to fine tune your vertical position in the water column without adjusting the volume of air in your BCD or drysuit. This is an especially important skill for photographers when hovering around a subject.