by Jon Kieren:
The goal of every avid diver is simple: Spend as much of your life as possible underwater. On open circuit SCUBA, we all have one major limiting factor, the amount of gas we brought down with us (along with no decompression limits, but this article will only address gas supply). Most new divers will have the same reaction when diving with a group, “How does everyone else stay down so much longer than me?” While this quickly fades after just a few dives as the beginner starts to be more comfortable, their breathing will relax a bit, and they are diving just as long as most of the others in the group. However, there are always those exceptions in the group that are able to stay down twice as long as everyone else. What are they doing that’s so different? Do they have gills? Well, no, but some of it is simply physiology. Small people with tiny lungs simply breathe less. Their smaller bodies require less oxygen for metabolism, and it takes far less gas volume to fill their lungs. Much of the rest stems from these three simple tricks.
- Relax. This is the hardest part for newer divers. Being underwater is both exciting and also a bit stressful at first. When people are excited, their breathing rate tends to increase. As you breathe faster, you tend to breathe shallower. Fast shallow breaths are very inefficient for gas exchange, and your body starts to build up carbon dioxide (CO2). As CO2 builds up, your body’s natural response is to increase your breathing rate. It’s a vicious cycle that results in a vastly increased air consumption rate and shorter dives. Relax and focus on your breathing, with extra attention on the exhalations. Make sure you are ridding your body of all of the built up CO2, and you will see a drastic improvement in your air consumption.
- Slow Down. Scuba diving is not a race. We know it’s exciting and you want to see as much as possible, but you’ll actually see MORE the slower you go. Swimming fast means you’re working harder and breathing harder, which means you’re breathing through your tank faster. If you see something amazing, don’t chase after it, let it come to you. Critters don’t like to be chased around the ocean, and you’re probably not going to be able to catch whatever it is anyway. Slow down and take your time and you’ll be able to stay down significantly longer, and in turn see more.
- Get yourself weighted properly. Many divers, both new and experienced alike, have a horrible habit of diving over-weighted. Their thought process is typically “I’d rather have too much weight than not enough, because I can always add more air to my BCD.” While to some extent this is true, and you can become neutrally buoyant by adding more air to your BCD, your air consumption will suffer. This happens for two reasons, both which take a brief physics review to explain. First of all, adding weight to a diver increases the diver’s mass. Even though you have added air to the BCD to counter the gravitational pull by adding buoyancy, the diver’s mass has still increased. Increasing a divers mass also increases his inertia, meaning it requires more force to propel the diver through the water. More force means the diver’s body will need to metabolize more oxygen, creating more CO2, increasing the diver’s breathing rate. Not only does over-weighting increase a diver’s inertia, but it also will have a negative impact on the diver’s trim. When a diver falls out of horizontal trim, they are faced with increased resistance when trying to move through the water. More resistance means it will require more force to move the same distance. Starting to see how diving over-weighted can seriously impact a diver’s air consumption?
Relax, slow down, and get properly weighted and you’re on your way to improving your air consumption. Just like anything, practice makes better, and the only way to truly improve is to get out there and dive as much as possible. Working with an experienced instructor can help get your weighting, trim, and buoyancy control dialed in, while the rest just comes from experience.