Knowing how much weight to use when freediving is vital. Using more or less than the right amount can have a negative impact on your dives and it can also be life-threatening. In the new episode of The Complete Guide, Alchemy partner & freediving instructor Pavel Tomm, looks into weighting & buoyancy and shares his tips on how to calculate the right amount of weights for you, depending on your individual needs.

A Bit Of Physics First

Today we're going to talk about buoyancy and weighting for freediving, to understand this principle, make your dive easier, more efficient, and safe. There are two forces acting on an object in the water, it's the weight of the object and the buoyancy, the buoyant force. The buoyant force is equal to the weight of the water which is displaced by the object. In this case by your body. I guess that all of you know that you can have some difficulties diving head down, especially in beginning, that's because the water is pushing you back up to the surface. How to overcome this problem is to develop a proper technique, have a perfect duck dive and know how to descend, it's not by overweighting yourself. Overweighting is dangerous.

Three Types Of Buoyancy

The first one is positive buoyancy. It means that you float, the water is pushing you back to the surface.   It means that the buoyant force is greater than your weight. Then is the neutral buoyancy, which means that both of these forces are equal. At some level, at some depth, you can theoretically stay forever, you're not sinking, you're not floating.  And then of course it's the negative buoyancy when your weight is greater than the buoyant force and you're going to sink.

Depth & Pressure

The deeper we are, the more are our lungs getting compressed, which means that the buoyancy is changing during our dive. This is something that we can use as a benefit for our deep dives because in beginning we need to use quite a lot of power to overcome the buoyant force,  but at some point, we get neutral and negative and we start to sink. After the turn is the same story. In the beginning, we need to move, the last few meters under the surface we can stop moving, and the water is just pushing us back to the surface.


It's important to know that as soon as you set up your buoyancy, as soon as you set up your weighting, you are inhaling always a consistent amount of air. Especially in beginning, it's a full breath. If you're not doing any simulations, we are diving always with full inhale.

Body Type & Water Density

All of us are different, we have different proportions, someone is more sinking, someone is more floating.  This is something that will determine your weighting requirements. Shortly, the tissue is floating, muscles are sinking. Freshwater is less dense than seawater. But also the salinity of the oceans and seas is changing, so you will need a different amount of weights in different seas. Shortly in the freshwater, you need much less weight than you will need in seawater.

Wetsuit Thickness

The thicker the wetsuit is, means more weight you need to use. It keeps you warm but you need to use more weights. Remember, the wetsuit is compressible, so as you descend the wetsuit is getting compressed and after the turn on the bottom you become very heavy. So that's why if you look at competitions if we're trying to dive very deep, we try to use very thin wetsuits. Not only wetsuit, but every other piece of equipment is also affecting your buoyancy. So it is important, always, if you change anything, you will check your buoyancy again.

Dynamic Apnea

In the pool, you want to be neutral, somewhere in between the bottom and the surface. You want to set up your buoyancy as perfectly as you can,  to swim horizontally, without using, without wasting some energy. How can we do that? You have full gear on, you have your wetsuit, you have your fins, you have the weighting system. You are taking a deep inhale, you use the wall, you do the push wall, maybe one or two kicks, and then you glide.  Now, you need to be really patient and you really need to wait till the point you stop, because then you're going to see if you sink or if you float. If you end up on the surface, if you floating,  you need more weights, otherwise, you keep pushing yourself down to stay under the water, and you are creating a drag. If you are too heavy, you sink. Of course, it doesn't make sense to dive when you are too heavy, because then you are like a frog. What is a really good idea, what kind of weighting system is a good idea to use during the dynamic in the pool, it's neck weight, because what we want is to have as much weight as possible close to our lungs. If you have just a weight belt, it wouldn't be perfect. You can make one by yourself or you can buy some sophisticated one, some special neck weight designed for dynamic disciplines,  when the weights are really on your back, above your lungs. Then your gliding can be just perfect.

Deep Freediving

Deep diving is a different story. We don’t want to be neutral one meter under the surface like we are in the pool, because we want to relax on the surface. Overweighting is dangerous as I told you in beginning, but it's also less efficient. The dive, the beginning, your duck dive, could be nice, could be easy, but you can't relax at the beginning of your dive. Imagine yourself floating on the surface or trying to relax on the surface while you keep sinking. It doesn't make any sense. So we need to set up our buoyancy in different ways, we want to be neutral much deeper. So what you need to do in the beginning, how you can test this, is to be on the buoy, let it go, stay vertical,  take a breath, do passive exhale, and now you cannot sink. The surface must stay somewhere on your eye level, floating. If you start sinking you are way too heavy and you should change it. It's dangerous well, as I told you beginning could be nice, you have a nice and easy duck dive,  but after the turn, you become very heavy and your ascent is getting more difficult, you need more energy and it can result in a blackout.

How To Set Your Weights

If you want to dive deeper, what we really need to know is how deep exactly are we neutral. This is important for us to know because we want to know where we can start a freefall. If you don't know that and you start freefalling too early, the freefall is getting very slow and you're wasting a lot of time. If you start freefalling too late, you're wasting a lot of energy. So how can we really set up the buoyancy, how can we really check how deep are we neutral?  What you need to do is to take a big breath,  and again, always it needs to be a deep inhale, and you slowly descend down to let's say 10  meters. Then you turn, so you are head up, slow stop the moving of your body,  you don't move at all, do like an okay sign around the line, and now wait, count to 10. And you will see, if you sink, you are too heavy, if you float go a bit deeper and check it again. This can really take some time and it's really normal that it takes few dives. You can use it as a warm-up, it's quite a good idea.


Remember, it's a good idea to set up your buoyancy somewhere approximately one-third of your dive. So if you're diving to 30 meters, you should set up your buoyancy to 10 meters. 10 meters should be the minimum, otherwise, you are too heavy, and you are overweighting. If you dive deeper, maybe your buoyancy could be also a bit deeper, which means that you need less weight. Always you changing the locations you freedive,  you change any kind of equipment, you need to check it again. Using different wetsuits, your buoyancy will be different, you're diving in different seas, your buoyancy will be different.  Use it as a warm-up, and do it always. So, thanks for watching, I hope it helps you a bit and I'm pretty sure it can make your dive more efficient and safer.

Alchemy V330
Pavel's Carbon Freediving Fins Of Choice

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