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10, Oct, 2013

The importance of good buoyancy

Posted in Course News, Diving News, Latest News, PADI Courses by kimmy

The Instructor team here at Scubafish would like to introduce the first in a series of Handy Tips for beginner (and not-so-beginner) divers. When asked what they wanted to start with – the answer was unanimous – the importance of good buoyancy!

Have you noticed how some divers seem to move effortlessly, gliding through the water with barely a kick and coming up with 100 bar or so still left in their tanks? Or seen a divemaster hovering upside-down face to face with a leopard shark? Or hovering in a buddha-type pose with crossed fins? This is all the result of proper buoyancy control, and here we shall share our knowledge with you!

 

What are the advantages of proper buoyancy control?

  • Improved air consumption – because you will expend less energy, you will use less air!
  • Safer ascents – you’ll be able to make Safety Stops with ease and maintain controlled ascent rates
  • Less weight to carry
  • You won’t damage marine life
  • You won’t harm yourself on marine life
  • More comfort in the water
  • More control
  • Increased confidence
  • You’ll look like a pro! (and less like a bull in a china shop!)

 

buoyancy

 

BCD’s and buoyancy

The function of a BCD whilst you are diving is to maintain neutral buoyancy and achieve a sensation of weightlessness.

Ideally underwater you should barely have to use your BCD – you may have to add a very small amount of air at the start of the dive to achieve neutral buoyancy, or compensate for the increased pressure at depth, but that is the only time beneath the surface that you would press the inflate button. The most common error or inclination of beginner divers or out-of-practice divers is pressing inflate to go up.

DO. NOT. PRESS. INFLATE. TO. ASEND… EVER!!!

Your BCD is NOT an elevator! You are not supposed to rocket to the surface. The air in your BCD will expand as you ascend, leading to an out of control ascent, and possible DCS.

Allow time for air to move around your BCD when you inflate, there will be a slight delay of a few seconds, so inflate only in small bursts and be patient, you can always add another small burst if required. Many divers press the inflate button repeatedly in short bursts but quick succession as they did not feel the difference immediately.

Your BCD should also fit you correctly – it should hug your body, and not move independently around it.

 

Weights and buoyancy

Many divers choose or prefer to dive overweighted, and then add air from their tank to their BCD to compensate for this. This pushes the torso up, drags the bottom half of the body (from the hips) down, therefore effecting streamlining. This diver uses more air from their tank, and more effort since this body position presents a greater surface area to deal with the water resistance.

It only takes a moment to complete a buoyancy check at the surface at the start of your first dive – and for the conditions around Ko Lanta, our tank size and wetsuits, the general recommendation is to start this check with approx. 5% of your body weight. All our instructors and divemasters carry extra weight with them should you require it.

Divers are meant to descend slowly, with a big breath out, allowing us the time to equalise and adjust for neutral buoyancy. Overweighted divers plummet down, often hitting coral, or stirring up the sand below them with their fins.

Another common issue is deflating or letting air out of the BCD – remember to raise the hose as high as possible above you, and tilt your upper body into a more vertical position again to release this air. Many divers believe they have let the air out, but the air has become stuck in the hose or jacket.

Trim is where you wear your weights, and is different for each individual. Some divers wear the weights in the front (many integrated weight pockets sit here), some prefer weights at their back, or distributed evenly all round, some divers like to wear a weight on their tank band, or ankles etc. It is merely practice that determines the correct positioning of weights for you.

 

buoyancy

 

Body Positioning and Buoyancy

If you are correctly weighted and neutrally buoyant then you should be swimming horizontally, leaving just your head and shoulders to deal with resistance of the water and expending less effort and energy. When we dive whichever way our head points and we kick we will go. So if you move into more vertical position to check your gauge or look at something stop kicking, and hover!

Hands – we use our hands underwater to check gauges, wear computers, hold cameras, point at fish etc., not to flail around!

Divers do not use our arms/hands to swim when diving. Flailing your arms around underwater is not only ungainly, it can be dangerous, causing you to knock off your buddy’s mask, pull out their regulator, smack into each other, knock against coral, and generally waste energy, effort and therefore air. Try clasping your hands in front of you, folding your arms, holding onto your bcd straps – anything to keep those arms still!

Kicks – we are not riding a bicycle – so your kick shouldn’t look like you’re pedalling! This takes a lot of effort, and produces very little thrust or movement. The correct fin kick technique is long, slow and uses the entire leg, not just the knee down. Perhaps you’ve noticed many dive guides using the flutter kick? Instead of kicking up and down, these divers appears to occasionally sweep their legs in a more horizontal position, with their feet often higher than their knees. This is a highly efficient finning technique and causes very little disturbance to sandy or fragile bottoms.

 

Breathing and buoyancy

When a diver is neutrally buoyant adjustments and compensation are made using our lungs. A big breath in will enable us to rise, and a big exhalation will enable us to sink slightly.

The normal breathing pattern we employ on land is not quite sufficient to create this effect. You need to breathe deep enough that your lungs expand and create an air pocket. Breathe as deeply as you can to best feel this effect.

Relax – if you are tense you are probably holding some air in your lungs still, and not breathing deeply. Visualise and take some deep breaths before your dive.

Practice! Practice! Practice!

Practice really does make perfect, and there are some great exercises you can slip into your dives to improve your buoyancy. Scubafish strongly recommend the Peak Performance Buoyancy Adventure Dive or Specialty Course to help you master these skills, especially if you are considering photography or wreck diving.

 


 

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