Let's Talk About BCs (part 3)

Okay, I know you have had enough about BCs but hey, the more you know the better you'll dive. So let's submerge ourselves into this week's tip: Controlling Loss of Buoyancy at Depth. Remember when I told you this was the least important feature of a BC? Here's why:

Back in the early days, when Moby Dick was a minnow, divers never wore BCs. That's right folks, guys like Jacques Cousteau never wore a BC! All he wore was a back plate and harness to hold his tank on. Impossible you say? Well here is how they did it. They knew that wet suits were going to make them float so they put on a weight belt to almost compensate for the suit so that they could almost sink. They then strapped a steel tank to their backs and jumped in. The steel tanks added a little more weight to the diver and they were able to comfortably and controllably sink. As the divers began to breath down the air in their tanks the weight of the steel tank would gradually get lighter. When they were down to 500 psi of air in the tank it didn't weigh enough to keep them under so they were forced to come to the surface where their suit would expand and they would float with ease.

So Why Do We Wear A BC?

Sadly enough it is because we don't dive like Jacques Cousteau. With the way most instructors teach today students are generally not given the care and experience that is necessary to make a good quality diver. Let me explain, it's easier to slap a bunch of weight on someone and toss them in the water and give them the ability to float if need be by pushing that little button on your BC. If we don't teach you that way it takes a lot longer to get your weighting proper and to train the student how to correctly use his/her own buoyancy to control themselves in the water. Don't believe me? Most folks who do a lot of diving will eventually learn to shed the excess weight and use the BC very little.

Don't get me wrong, I don't agree with not teaching the student properly this is just what I have seen from the industry. But enough about that, let's talk about proper BC usage.

With the styles of tanks and suits that are made today buoyancy can be a real issue. For instance in order to use an aluminum tank you must be over weighted at the beginning of your dive so that when your tank is down to 1200 psi and begins to be positively buoyant it won't pull you up out of the water. Well when we start our dive we are going to sink quite easily due to the extra weight. That is where the BC comes in, we need to add a little air at depth to even out our buoyancy. We will also get more suit compression the deeper we dive. This too will make the weight on our belts feel heavier. Why? Because the suit is smaller and not as buoyant as it was at the surface thanks to water pressure and the compressing of the gases in the neoprene. So again we need to add a little puff of air to equal things out.

BCs also make folks feel more comfortable in the water. Generally SCUBA courses don't teach strong surface skills because they are convinced that a BC at the surface will be sufficient. Nothing could be further from the truth. If you can't float on the surface without your BC then you have too much weight on.


The important thing to understand about BCs at depth is that they are used to compensate for loss of buoyancy. Suit compression should be the major reason that you will need to add air to your BC at depth. If you are weighted properly then you will only need a very small amount of air in order to regain neutral buoyancy.

So until next week stay wet and stay warm.

Return to Diving Tip List.