Improve your Buoyancy: Part 2 – Weights

A thorough understanding and practical application of neutral buoyancy is the most important skill for safe and enjoyable diving. What are the key factors influencing buoyancy control, and how can you improve your neutral buoyancy skills?

Many different things factor into perfect buoyancy, each going hand-in-hand. If you are lacking in one area, your overall buoyancy and comfort underwater will be affected. This comprehensive guide is split over 4 parts, each deep-diving into the key elements to improve your buoyancy control: breathing control; weighting; use of the BCD; trim and finning techniques.

We recommend reading all parts of this series to see if you are aware of – and using – these points to improve your buoyancy, even if you think you may have mastered certain elements.

Following on from part 1 where we discussed breathing control and the effect of breathing on buoyancy, in part 2 we will discuss the next step to improving your buoyancy control; Weighting. What factors can influence how many weights you may need and what are the signs of improper weighting that you should look out for?

One of the leading causes of struggling to achieve effortless neutral buoyancy is improper weighting, most notably overweighting. It is unfortunately common for instructors to overweight their students and for certified divers to overweight themselves, under the guise that carrying more weight than necessary makes it easier to stay underwater and avoid uncontrolled ascents. A potentially dangerous misconception that we will explain in a separate blog post soon.

It is important to be able to recognise the signs of being underweighted or overweighted. You should do weight checks often and not be afraid to play around with your weights with the help of a buddy or instructor. Most divers need less weight than they think. I can assure you that finding your perfect weight will significantly improve your comfort underwater, and make buoyancy control effortless. 

Factors that can Impact your Weighting

Firstly, it’s important to discuss the factors that can impact how many weights you may need to dive with. 

Breathing

One of the largest determining factors is your breathing and lung volume! Relaxed breathing around mid-range of your lung capacity instead of fully inhaling on each breath, not only makes it easier to control your buoyancy but also makes you less buoyant. Divers who struggle to sink at the beginning of a dive, but once down AND at the end of the dive are absolutely fine, are likely nervous or excited and holding their breath or not exhaling fully. Remember to be aware of your breathing. Read part 1 of this comprehensive guide here to further your understanding. 

Body Composition

The ratio of one’s fat to muscle mass. Muscle weighs more than fat, so someone who is lean or carries a higher ratio of muscle to fat is likely to be more negatively buoyant. Body composition can be influenced by genetics and previous or current exercise. It is difficult to tell how many weights someone will need just by looking at their outward appearance. 

Exposure Suit

Most diving wetsuits and some drysuits are made from neoprene or similar materials. They are designed and manufactured to hold pockets of air. A well fitting wetsuit will reduce the flow of water over the skin. The skin warms up the water immediately in contact and the air pockets act as insulation to stop the heat from escaping. The thicker the wetsuit, the more air retention, greater insulation and more positive buoyancy. New wetsuits will have more buoyancy than an older suit that has been continually compressed over dives.

Equipment

Dive equipment is not created equal in buoyancy. Buoyancy varies between brands and even models. For example, the steel backplate of some wing style BCD’s will be more negatively buoyant than the plastic backplate of standard jacket style BCD’s. Regulator sets also greatly vary in weight and buoyancy. Some brands state the buoyancy characteristics of their equipment, even creating specific models of equipment to be neutral, positive or negatively buoyant. 

Salinity

The salinity of the water greatly affects how much weight you will need. The greater the salt content in the ocean, the greater density, which leads to objects being more buoyant. For example, Egypt’s Red Sea is an area of very high salinity compared with the tropics of South-East Asia. Some divers report using half of the weight that they used in Egypt in other oceans of the world. 

Tanks

Steel vs Aluminium. Aluminium tanks are significantly more buoyant than steel tanks; meaning a full aluminium tank will be negatively buoyant and become positively buoyant when it is empty, while a steel tank will almost always be negatively buoyant, even when empty. 

Reminder: if any of these factors change before your next dive, or you are unsure, you may need to take a few kilograms more than you think. Be sure to analyse how you feel in the water with these weights, as detailed below. Perform a weight check as explained in your dive training course materials – also available online. In addition, you can check your weights during your safety stop, by releasing all of the air from your BCD and using your breathing to control your depth. If you have to breathe deeply to maintain depth, or have to constantly kick in order to not descend, you are overweighted.

Improve your buoyancy with our experienced instructors by joining a RAID Explorer 30 course on board our DiveRACE trips! The RAID course focuses on imparting important skills to improve one’s buoyancy. 

How to tell if you are improperly weighted

Overweighted

A diver who is overweighted will need to compensate by adding more air to their BCD. More air in the BCD leads to a greater increase and decrease in volume with minor changes in depth. You may feel as though you are constantly adding air into and removing air as you are diving, to compensate for this constant change in volume as you may not be aware of your changes in depth. 

You are likely sinking fast at the beginning of a dive and have a feeling of heaviness throughout the dive. Optimum horizontal trim will feel more difficult to achieve as the weights weigh down your lower body, and the greater amount of air you placed in the BCD will pull your upper body upwards, further exacerbating poor trim. Diving in a more vertical trim, with your lower body under your upper body, makes unwanted contact with the reef more likely. It will increase your drag in the water, rendering finning techniques less efficient, increase energy expenditure and raise your air consumption. 

Many overweighted divers do not add enough air to the BCD and end up diving negatively buoyant. They will often be constantly kicking to stay above the reef, using full lung capacity to hold them up and using more energy than necessary, all factors that will increase air consumption. Read part 3 (coming soon) for instructions on how to properly use your BCD for buoyancy control.

Underweighted

Being underweighted can also be an issue for some divers. Maybe you are diving in a new location with higher salinity than your previous dives, using different equipment and tanks, or have forgotten to log how many weights you used previously. Being underweighted can be noticed at the beginning of a dive if you are struggling to descend (remember to fully exhale!) or at the end of the dive/safety stop when your tank is close to empty. 

You may feel like you are underweighted if you feel the need to kick down at any point during a dive. Before assuming this and piling on the extra weight for the next dive, make sure that you are releasing air from your BCD AND fully exhaling, allowing yourself time to descend before taking your next breath. 

“I tried to release air from the BCD but there was nothing remaining/it did not come out“

A common cause of divers being overweighted is improper understanding and use of the BCD. Gasses can only rise underwater, so the release valve that you are using must be at the highest point of your body at that moment. 

For example, to use the inflator hose to release air, you must go into a vertical orientation extending the hose above your shoulders for the air to rise up and escape. Even a very slight angle forward will trap the air in the BCD on your back or under your shoulders. We often see divers trying to release air in a horizontal position, signalling that no air is coming out and that they must not have air left to release. A simple reminder to go vertical in the water leads to an ‘ah ha!’ moment as the remaining air can now escape. Read part 3 for more instructions. 

Now, we hope that this helped you gain a better understanding of how your weights can affect buoyancy?  Great! Part 3: How and When to Use Your Buoyancy Control Device, will be released shortly. In this chapter, we will discuss optimum BCD use for buoyancy control. How should the BCD be used to achieve neutral buoyancy and how can you tell if you are truly neutrally buoyant?
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