When I started freediving, I asked the same question nearly everyone does. This is, how much weight do I need? For a block of metal, lead can be expensive. You don’t want to buy more than you need, but you also don’t want to be caught short.
Freedivers wear lead weights to offset the positive buoyancy of their bodies and their wetsuits. To freedive comfortably, we use enough weight to help us descend to the point our lungs and wetsuit compress to the point we achieve buoyancy.
So why not just wear a bunch and call it a day?
There are several problems with being overweighted.
Being overweighted makes it hard to rest on the surface and breathe up properly before diving. If you can’t do either, you will shorten your breath hold resulting in lower bottom times.
Should you blackout at or near the surface, you will sink. While you should have a trained buddy to assist you, the added weight will make it harder for your buddy to do so.
Yes, you want to descend with the least effort possible to extend bottom time. However, if you are overweighted you just made the most dangerous part of your freedive more difficult.
When you are at depth, your lungs, gastrointestinal tract and wetsuit are all compressed. This makes you even more negatively buoyant. So now, at your most hypoxic point in the breath hold, you must work even harder to get to your next breath if overweighted. This is not an ideal situation.
So how much weight should I wear?
Everyone’s body composition is different. Bone and muscle density, fat content, lung volume, height and weight all affect buoyancy. Then there is water density. Salt water makes you substantially more buoyant.
The only way to accurately determine how much weight you need is through trial and error. I recommend buying a small number of weights to start. You can then rent or borrow some additional weight to finalize how much you need.
Begin with all your equipment in place while wearing an estimate of the weight you think you will need. Good starting points for an average-sized person will vary depending on suit thickness. They include:
3 mm: 1-2 kg/2-4 lbs
5 mm: 3-4 kg/6-8 lb
7 mm: 5-6 kg/10-12 lbs
Next, get in the water. Flood your wetsuit to ensure there are no air bubbles trapped inside. Then, with your head upright, take a peak inhalation (the maximum sized breath you would be diving with) just as you would if making a dive. Without sculling, finning or treading with your hands, you should float up around collarbone level. If the water is higher than your collarbone, remove some lead. If it is below, add some. Make your adjustments, then try it again.
Once you float at collarbone level on a peak inhalation, perform a relaxed exhale. Don’t push from your stomach but exhale to the point where you would if you wanted to get more out later. Think a big sigh.
When you do this, you should not sink. You will drop down and may even go below the surface. But you should stay at the surface. This helps ensure you will remain there should you experience a blackout.
Performing this simple check every time you:
Use new equipment
Freedive in a different body of water (fresh vs. salt)
Put on or take off a few pounds around the waist
It will help you to better determine how much weight you need to freedive. Your goal is to:
Achieve neutral buoyancy at 10 m/33 ft deep
Rest easily on the surface between dives
Use positive buoyancy to ascend with less effort
Allow enough weight to make entry and descent easily
Keep you safe in shallow water, where most blackouts occur
Notes about your weight belt
Your weight belt must have a quick-release buckle so you can:
Ditch the weight quickly in an emergency
Remove it easily and carry it at your side if you think you may experience issues during ascent or at the surface
Rubber weight belts will stay in place better over a nylon belt as you descend. When your suit compresses, a nylon belt will often end up around your chest.
Using smaller increment weights allows you to adjust your buoyancy more accurately. Weights in the 0.5-1 kg/1-2 lb range are ideal. This will also more evenly distribute the weight around your body and allow for more streamlined freediving. It will also decrease your effort and increase your bottom time.
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