By Landon Russell
One of the intellectual joys of SCUBA diving is the intentional application of practical physics; it’s a sport where the enthusiast benefits from conscientious applications of a simple pressure formula. While enjoying an introductory dive hosted by a fun tourist-guide, a scuba-launch service leaves this science mostly to the discretion of your guide. Becoming a knowledgeable diver and guide requires a working understanding of how changing pressures at increasing water depths also changes how you breathe and process your air. Remember; DO NOT hold-your-breath while diving, it’s a bad thing and you won’t like it.
Boyle’s Law is PV=c where pressure multiplied by volume is a constant: in other words, when you multiply the pressure surrounding a gas by the volume of the gas you will always end up with the same number. By decreasing the pressure (P) surrounding a gas, the volume (V) of gas becomes greater. By increasing the pressure surrounding a gas, the volume of the gas becomes smaller. This is demonstrated during a quick-course with a balloon as a visual guide which changes size when pressure is applied.
This simple physics formula affects all aspects of diving, including buoyancy, flow-rate, ear comfort requiring a pressure equalization to prevent barotrauma, air absorption through the lungs into the bloodstream at increased speeds while pressurized and the subsequent expulsion of the same air from the bloodstream at speeds relative to the measured dive pressures to prevent the dangers of expanding bubbles within the veins, which is a bubble-related decompression sickness known as “the bends.” These situations do NOT occur in “shallow” waters which typically are less than 30 feet under the surface. For tourist divers you may rest assured, and have confidence that your SCUBA experience is completely safe when the majority of your dive is in shallow waters. It is still OK to spend brief time in deeper waters following a guide, because this is a known science.
As a tip, you can spend literally ALL DAY in waters less than 15 feet deep, and you can spend several hours in waters less than 30 feet deep, and an enjoyable amount of time safely in waters 40 feet deep. Below 60 feet is considered a technical “deep dive” and is not for short-course beginners. The deeper you go underwater, the faster your body absorbs air. Decompression during a technical dive is only required if your body absorbs more air than it can expel, and your hired SCUBA guide who has studied and practiced this math for the required length of time to become a technically certified dive-master will not risk his own health much less to risk your health as the recreational dive client.
For your own safety, there is one typical guideline to follow when you plan your SCUBA trip; you should allow yourself a day between tank diving and your return flight, because when you dive, you absorb more air into your bloodstream which can react to the depressurized airplane cabin air which can result in “the bends”, DCS/Decompression Sickness while in flight. When you allow yourself a day to lie on the beach before you fly, you are allowing the additional air gained in your blood-stream while diving to normalize to the surface pressure (1 ATA). You will have a safe and healthy flight home by relaxing on-shore or by surface snorkeling in shallow waters during the last day of your vacation.
About the Author
Landon Russel is a webmaster, IT consultant and dive enthusiast who enjoys both saltwater and freshwater diving.