Divers seeking perfected scuba buoyancy can achieve precise and correct weighting through the application of several assessment methods. As the diver progresses in experience, whenever they change equipment or whenever they change diving environments (salt/freshwater) they should re-assess their weighting.
During the initial stages of diver development, changes in breathing patterns and increased relaxation underwater often also allow a slow progressive reduction in weights.
Our aim is to carry sufficient weight to allow us to maintain neutral buoyancy at any stage in the dive, without carrying an excess weight that has to be offset by adding extra air to our BCDs.
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How much scuba diving weighting is needed?
At the very most, we need sufficient weight to allow us to maintain neutral buoyancy at the end of the dive when our exposure suits re-gain buoyancy on the ascent and we have depleted a significant weight of gas from our scuba cylinders.
This is essential if we are to maintain safety stops and conduct a slow, controlled ascent from that stop to the surface.
How to confirm your scuba diving weighting
There are three primary methods for estimating, assessing and confirming our weighting requirements:
Basic weighting guidelines
–Estimate- We can follow a series of basic calculations, which incorporate the buoyancy of our exposure suit and body size to provide a rough estimate of our weighting needs (see below). This allows us to set up a weight belt in advance of our dive.
These calculations, often written in Open Water course manuals, tend to grossly overweight divers. They can be a useful starting point if change exposure protection, but they need to be greatly refined through more precise in-water checks.
7mm wetsuits w/hood: +10% bodyweight + 1.5-3 kg (3–5 lb)
Neoprene drysuits: +10% bodyweight + 3–5 kg (7–10 lb)
Trilaminate drysuits: +10% bodyweight +1.5–3 kg (3–5 lb)
Adjust weighting for human factors:
Women should add 4-5 lb of weight (~2 kg) if diving in saltwater or subtract the same amount for freshwater.
Men should add 6-7 pounds (~3 kg) if diving in saltwater or subtract the same amount for freshwater.
Quick pre-dive check
–Assess- Once we actually enter the water, we can confirm that our estimation was correct. This check ensures that we have sufficient weight to descend, but are not carrying a surplus, unnecessary weight. It is a simple, quick check that can be conducted before any dive. To carry out this check, conduct the following steps:
At the surface, take a deep breath and hold it.
Cross your ankles to prevent any instinctive fin movement (upwards propulsion).
Keep your arms against your body to prevent any instinctive sculling.
Hold your LPI vertically upwards and release all the air from your BCD.
You should now float at approximately eye-level in the water.
Exhale the breath that you were holding.
You should now begin to slowly sink.
If not, then add/remove weight until you do float at eye level whilst holding a normal breath and can sink when you release that breath.
Once this is achieved, add 1-2kg of weight to account for air use during the dive.
Shallow-water check
–Confirm- Whilst the pre-dive weight check gives us a fair idea of our weighting requirement, it does not account for air use during the dive. It is well worth conducting an accurate check that absolutely confirms your weighting requirement under these circumstances. To conduct a weight confirmation, follow these steps;
Attempt to hover neutrally buoyant at 3-5m depth, whilst breathing normally.
Deplete the air in your cylinder to 30 bar.
Slowly reduce the weight that you are carrying (small weights are best, for fine-tuning).
When you reach a stage that requires breathing adjustment (shallow breathing) to maintain your stop depth, then you have reached your absolute minimum weighting.
Once you confirm your minimum scuba weighting requirements, you can be confident that you will have enough weight for your initial descent, and enough weight to hold a safety stop with minimum air remaining in your cylinder. Nothing more, nothing less. Your progress towards effective buoyancy now has a strong foundation and will be considerably easier.
Currently residing in Subic Bay, Philippines; he has amassed more than 10,000 open-circuit and CCR dives over three decades of challenging diving across the globe.
Andy has published numerous diving magazine articles and designed advanced certification courses for several dive training agencies, He regularly tests and reviews new dive gear for scuba equipment manufacturers. Andy is currently writing a series of advanced diving books and creating a range of tech diving clothing and accessories.
Prior to becoming a professional technical diving educator in 2006, Andy was a commissioned officer in the Royal Air Force and has served in Iraq, Afghanistan, Belize, and Cyprus.
Currently residing in Subic Bay, Philippines; he has amassed more than 10,000 open-circuit and CCR dives over three decades of challenging diving across the globe.
Andy has published numerous diving magazine articles and designed advanced certification courses for several dive training agencies, He regularly tests and reviews new dive gear for scuba equipment manufacturers. Andy is currently writing a series of advanced diving books and creating a range of tech diving clothing and accessories.
Prior to becoming a professional technical diving educator in 2006, Andy was a commissioned officer in the Royal Air Force and has served in Iraq, Afghanistan, Belize, and Cyprus.
Originally posted 2011-07-01 14:53:51.
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