It’s really brave to be considering the subject of physics when you’re learning about scuba diving, but it’s also a required component of every diving class curriculum. Physics can be intimidating; you might have studied it in high school or college and forgotten most of what you learned. However, let’s try to refresh our memories and apply that knowledge to a favorable scuba diving experience.
Diving as a sport involves putting people in an environment that they aren’t a natural part of. We all realize that we can’t breathe underwater and that water and air are fundamentally different. There are some rules of diving and being under the water, surviving there can be dangerous or deadly if you don’t learn the rules of the game.
It’s not quite as simple as taking a tank of compressed air with you under water. Everything you think you understand about being underwater is different. You see and hear differently, gravity works differently, colors are different, water conducts heat differently, and lastly but most importantly, water is denser than air. Since water weighs 800 times as much at air at sea level, there is an effect that occurs building up pressure as you dive. Since the body is made up of a lot of water, you won’t be crushed, but that pressure will affect the gasses inside your body. By getting compressed more the deeper that you dive, so the impact on your body must be taken into account and understood.
Buoyancy is a major term in diving. When looking in the dictionary, it has to do with the tendency of an object to remain afloat in a liquid. Generally, you should remain afloat based on your body weight. In order to dive down further in the water you need to do something, and to rise back up you need to take action. This is normally done by controlling the air in your lungs. There are also devices that are involved with your tank of air called a Buoyancy Compensator (BC), also called a Buoyancy Control Device (BCD). The BC gets what it needs to control your buoyancy from the tank of air you carry with you and can control your buoyancy at the various depths through which you may dive. This is also a safety device should you need to ascend quickly.
Several factors that control your buoyancy and you should learn about all of them. Most of them have to do with weight, what you carry with you, how much air is in your tank and whether you are diving in fresh or salt water.
Being aware of the interaction of gasses in your system is the most important item. The oxygen and nitrogen will interact and affect your body. Oxygen is good and nitrogen is bad generally.
Nitrogen is worse because more of it gets into your body as you dive deeper and needs to be expelled as you ascend. The rate at which your body can expel it needs to be taken into consideration and the controlled ascent is preferable so that your body can handle the nitrogen properly. Otherwise, that thing called the bends happens.
Other considerations that should be understood involve: understanding gas laws, considerations for high altitude diving, understand how light, vision and sound are affected underwater, and how heat loss affects your body underwater.