Finding the right number of weights for your dive can determine whether you have a great dive or a disaster of a dive. If you realize you have the wrong number of weights after jumping into the ocean it can be annoying or even dangerous. You will need to consider a number of factors to know if you are properly weighted for diving and learn how to make a weight belt for diving. Luckily as a beginner, instructors will often carry a couple of extra weights for you as they help you figure out your imaginary scuba weight calculator for that perfect diving buoyancy!
In this article, we will explain everything you need to help you determine the correct number of weights for your dive. This post aims to help you plan your weights before jumping in for a dive and be able to confidently say I know I am properly weighted for scuba diving if I..!
I know I Am Properly Weighted for Scuba Diving if I Do a Buoyancy Check!
Of course, there is one definitive way to determine if you have the right amount of weight – a buoyancy check on the surface. However, this should be done with a steel tank or an aluminum tank that is nearly empty.
There are 6 simple steps to a buoyancy check on the surface:
1. Get fully kitted up and wear your best guess at the weights required. Base this either on a weight calculator, or from previous experience, or the recommendation from your guide.
2. Enter the water and inflate your BCD on the surface.
3. Take and hold a normal breath of air – THE ONE TIME YOU WILL EVER HOLD YOUR BREATH.
4. Empty your BCD completely and allow yourself to sink.
5. If the water level sits at eye level while holding that normal breath of air in your lungs, then descend when you exhale. This means you are correctly weighted!
6. If you are sinking while holding that normal breath in your lungs, then you are overweighted and are using too many weights. Try taking off some weights.
If you are floating on the surface and cannot sink to get to eye level with the water, then you are underweighted and do not have enough weights. Try adding a weight.
Read More: Why Do We Need Weights in Scuba Diving?
We would also recommend doing this same check post-dive, with a near-empty tank. This will give you a better indication of the correct amount of weights needed with a more buoyant tank.
How do we know how many weights we need?
The number of weights to wear depends on a large number of factors. These include:
Type of Water – salt is more buoyant than freshwater
Tank Material – Aluminium tanks will start off negatively buoyant but will become positively buoyant as you consume the air. This means you will need to account for the buoyancy change during your dive. Steel tanks, however, will remain negatively buoyant through the dive.
Weight of the Diver’s Body – larger people generally require more weight though if you have a lot of muscle mass, then this is denser and will sink easier.
Body Fat Percentage – Fat is more buoyant and floats, so people with more body fat often float on the surface easier.
Type of Clothing Being Worn – A full-body 5mm wetsuit will be a lot more positively buoyant than a string bikini. A dry-suit will be even more buoyant.
Experience – Experienced divers with developed breathing techniques can reduce the number of weights required
BCD – Different BCDs have different lifting capacities. This affects the amount of weight required.
Regulators – Even your regulator can have an effect on weighting. Heavier regulators and 1st stages will help reduce the amount of weight required.
Does a SCUBA weight calculator exist?
Some people have tried to produce mathematical calculations on how much weight you should carry. In recent years mobile apps have appeared to claim to be a scuba weight calculator. After entering all the parameters, they will give you an estimate of how much weight you should carry.
While tools such as these sound perfect, they are still no replacement for experience. Every time you dive, you should make a note of how much weight you used and what you were wearing. Take note of the conditions too. For regular divers, it will quickly become second nature and you will naturally select the required weights based on your equipment configuration that day. For the occasional leisure diver who only dives once a year however, calculation apps provide a good starting point that can be adjusted from thereon. If in doubt, always ask your instructor or divemaster for their assistance, as most professionals can give you a calculated guess based on your body shape and equipment.
What if the weights are wrong?
At some point, everybody gets it wrong. Too many weights may increase your drag and air consumption as you try to compensate for it by adding extra air to your BCD or breathing in to float. But being ‘over-weighted’ will generally not cause a big problem. Not enough weights, however, can make your dive very uncomfortable and possibly dangerous.
If you notice that you have a lot of difficulties descending at the start of your dive, then the safest thing to do is to either abort the dive or go back to the boat to get more weight. This is important as you also want to make sure you have enough weights to be neutrally buoyant during your safety stop at the end of your dive.
The main issue with being ‘under-weighted’ during your dive with an aluminum tank is if you end up making a rapid or fast ascent to the surface. As you dive, your tank will slowly start to pull you up. Usually, you will release some air out of your BCD to counteract the positive buoyancy. However, if your BCD is completely empty and the tank is pulling you up to the surface too quickly, then you may have a risk of Decompression Sickness (DCS) or Lung Overexpansion (LOE).
DCS is caused by going up to the surface too quickly without allowing the absorbed nitrogen to escape from your body, while LOE is caused by accidentally holding your breath as you go up. Figuring out that you are under-weighted during a dive can potentially be stressful leading to dangerous situations.
Modern diving techniques and equipment require you to be correctly weighted. If you are overweighted, you will be diving inefficiently and will struggle to stay off the seabed and coral. This will lead you to waste air. If you are underweighted, you will struggle to descend and may find yourself constantly swimming down to stay underwater. This will also lead you to waste air.
Choosing the correct amount of weight is therefore vital. Regular divers will instinctively know how much weight they require that day. The occasional diver, however, should make an effort to record in their logbook how many weights they used on a dive, what they were wearing, and if they had any problems being over or under weighted. While you may see it as hassle writing such comments in your logbook, you will be thankful 6 months later when you’re preparing to go diving again.
However you do it, take weighting seriously and don’t be scared to ask for more weight or abort a dive if you are incorrectly weighted. Your journey to perfect buoyancy is wholly dependant on correct weighting, so treat it as important as any other pre-dive preparations.