Perhaps you just need more ballast because your anatomy requires it.
Either way, when you do a proper buoyancy check, you’ll know that you are diving with the amount of weight you need to offset the positive buoyancy of yourself and your gear.
As a rule of thumb, if that amount exceeds 8lbs (3.6kg) the practice of placing all your ballast either on your weight belt or in the ditchable pockets of a BCD while at depth can be dangerous.
You may be wondering why. It’s because, if you were to ditch all that weight at depth, you could possibly be placing yourself into a situation where you could go into an uncontrolled ascent the moment you lose all the ballast that was keeping you down.
Uncontrolled ascents can have catastrophic effects on a diver.
Things like an arterial gas embolism, decompression sickness, or a reverse block are all real dangers. There is also the danger of being finding yourself in an uncontrolled ascent while hearing the sound of an oncoming boat.
If you still choose to store all your weight in a system that makes it ditchable, you need to think about the possibility that you could accidentally lose all your ballast.
I’ve seen this happen many times over the years. A belt becomes loose or the Velcro that holds a weight pocket in place becomes worn and doesn’t hold as tightly any more. This could cause a diver to unknowingly lose all their weight.
The bottom line is that if you need a lot of weight to be neutral at the end of your dive, suddenly losing that weight can be dangerous. You need to think about where you are placing the weight that you need and why you are doing so.
When You Absolutely Should Be Able to Ditch Your Weights!
There is one scenario where you absolutely need to be able to ditch SOME of your weight. It’s when you are diving deep (over 100 feet / 30 meter) and using a wet suit that is 5mm thick or more.
Why? Because the wet suit will compress at depth. Neoprene is a material that is made up of microscopic nitrogen bubbles. Those bubbles compress the deeper you go.
This means 2 things:
- Your wet suit will not insulate as well at deep depths as it does at shallower depths.
- More importantly, because all those tiny microscopic bubbles are compressed, the suit will also be less buoyant at depth.
Because of this, you’ll need to compensate for the positive buoyancy that your suit loses at depth by adding gas to your BCD. It also means that you are more negatively buoyant at depth than you are when you are shallow.
Therefore, it is important for you to be able to ditch some of your weight at depth.
Should you experience a catastrophic event that renders your BCD useless, you may not be able to swim your way up to the surface because of the additional negative buoyancy caused by the compression of your wetsuit.
In this scenario, ditching some of your weight could save your life.
The above scenario poses a difficult decision. You may need to ditch some weight to be able to get to the surface but doing so puts you in a position where, once your suit becomes more positively buoyant, you could find yourself in an uncontrolled ascent.
Yes, it is a catch 22. The way I see it is, I would rather be slightly positive than extremely positive due to the fact that I had to ditch all of my ballast. This is why I think it is important to make only some of your ballast ditchable rather than all of it. The amount that you ditch should not exceed amount of buoyancy lost by the suit.
When Things Go Wrong: Abrupt Changes in Buoyancy
I have a confession to make. When I first started diving I thought that the chances of having a failure of your BCD or anything else that would severely affect your buoyancy was unlikely. Especially if you maintained your gear and always went diving with relatively new gear.
Boy was I wrong!
First, I had a dive where my own BCD broke at the elbow where the low-pressure inflator connects to the bladder.
About a year later I was doing a dive with a student and her high-pressure hose burst while on the dive.
A couple of years after that, I had a different BCD’s dump valve completely come off when I pulled on it to release some gas.
Over the years I’ve heard multiple stories just like these that happened to other people.
I’m telling you this because, if you dive long enough, you will experience equipment failures. It’s a part of the sport. Fortunately, if you are properly trained these are usually just minor annoyances as they were for me and my student.
There are several scenarios where your buoyancy can change quite rapidly and without warning. As a diver, it’s important for you to know about and plan for the possibility of these scenarios.
Equipment failures that can cause abrupt Buoyancy changes
Catastrophic equipment failures are not common but they can happen and it is important to consider these unlikely scenarios and how to handle them.
Becoming Positively Buoyant Unintentionally