Welcome to Spearfishing School Part 13 of our 80+ part series written for people new to spearfishing. This blog is free for my readers and so is access to Spearfishing School during the beta stage. If you learn something here, sign up for our email list and share this page with someone that is looking to learn about spearfishing. It is a free way to say thanks.
Yes, you need a weight belt. The weight belt is used to set your neutral buoyancy. Here is how.
Why do I need a weight belt?
Your spearfishing suit is buoyant. In other words it floats. How much it floats depends on the thickness. The thicker your suit is, the more buoyant it is.
Let’s use a number line to illustrate how this works. Positive numbers represent positive buoyancy or floating. Negative numbers represent negative buoyancy or sinking. The zero is neutral buoyancy – You are suspended in the water without floating up or sinking deeper.
OK. Here is an example. Say I am diving in nothing but a speedo. My body’s natural buoyancy plus the air in my lungs determines if I float or sink. If I exhale completely I’ll sink. If I take a deep breath and hold it I’ll float. My Neutral Buoyancy is at or near the surface. Remember, it depends on how much air is in my lungs. On our number line, with air in my lungs my zero (neutral buoyancy)point is about 3 feet deep. That puts me at a 3 on the number line. On the dive down I will be fighting buoyancy for the first 3 feet. When I get to 3 feet I will be at my neutral buoyancy point. If I go deeper I will start to sink. I sink because gravity is stronger than buoyancy below the neutral buoyancy point.
Now add the Spearfishing suit. Let us say it adds 50 points of buoyancy. Now I am at 50 on the number line. That moves my neutral buoyancy point to 50’ deep. I could let all the air out of my lungs and not sink. If I could get my fins underwater, I would have to fight buoyancy all the way down to about 50 feet. If I stop short of 50 feet I will float back up to the surface. If I want to spearfish at 30 feet I would use up all my breath continuously kicking to stay down at that depth. Here is where the weight belt comes in. The weight belt allows us to set our Neutral Buoyancy point. We add weight to the belt to lower our score on the number line. Say we add enough weight to make our score drop to 30. A good depth for neutral buoyancy is 30 feet. If I want to hunt at 40 feet I fight buoyancy on the way down then when I pass 30’ I stop kicking and sink to 40’. When I’m ready to come back up I kick to get up past 30’ and buoyancy starts to help me get back up.
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