How Long Can You SCUBA Dive?
Candace Reno November 12th, 2019 Posted In: Articles Tags: SCUBA
How Long Can You SCUBA Dive?
SCUBA diving is an amazing journey underwater to see and do things that many people never have! But, just how long can you SCUBA dive?
The amount of time you can spend underwater SCUBA diving is mainly dependent on two factors: nitrogen absorption and air consumption. Other factors that may influence how long you can spend SCUBA diving underwater might include water temperature, time limits set by boat operators, currents, or weather conditions, among others.
SCUBA Diving and Nitrogen Absorption
The depth at which you dive affects the question “how long can you SCUBA dive” because you absorb nitrogen. As you dive down, the pressure increases by one atmosphere every 33 feet (or 10 meters). You breathe compressed air from a SCUBA tank, which contains 21% oxygen and 79% nitrogen (with a small percent of other gases). With the increase in pressure at depth, the partial pressures of both oxygen and nitrogen increase which causes both gases to be absorbed by your tissues. The oxygen you absorb while SCUBA diving is readily used by your organs for metabolism. Nitrogen, however, is not used by your organs and becomes stored in tissues. Our bodies can only handle so much nitrogen absorption before the risk of decompression sickness sets in. Thus, recreational diving has adapted dive tables based on the old U.S. Navy dive tables, which, if you follow, decreases your risk for decompression sickness.
Nitrogen is absorbed more readily at deeper depths, making how long can you SCUBA dive dependent on how deep you are. For instance, the time you can spend SCUBA diving at 100 feet is 20 minutes whereas if you limit your dive depth to 35 feet, you could stay for 205 minutes (if you had enough air). These time limits are found on the recreational dive tables. Proper dive planning will help you plan how long you can SCUBA dive based on your dive site. Dive computers are also based on the recreational dive tables and decrease the chance of accidentally exceeding your limits.
SCUBA Diving and Air Consumption
Based on similar diving physics as above, how long you can SCUBA dive is also dependent on air consumption. The deeper you dive, the faster you will burn through your air. Why do you use so much more air at depth? With the increase in pressure every 33 feet, there is an inversely proportional volume change and directly proportional density change. For instance, a dive to 66 feet is a dive to 3 atmospheres. The volume would decrease by 1/3 and the density would increase 3 times. This means every breath you take in at 66 feet is 3 times denser than at the surface. Thus, a shallower dive will increase how long you can SCUBA dive because your air will last longer. There are many wonderful SCUBA diving sites in shallow water that can be explored for a long time.
Another factor to consider for how long can you SCUBA dive is water temperature. Your body loses heat to water 20 times faster than it does to the air. Thus, when you are submerged in water, such as when SCUBA diving, you lose heat to the water. Without proper thermal protection, you can become cold while SCUBA diving even in water temperature that would seem perfect for a swim. I have been diving in 80 °F water temperature before while wearing a 3 mm wetsuit and still became cold at the end of a one-hour dive.
SCUBA Diving wetsuits help us maintain body heat by trapping water inside the wetsuit where our bodies heat it up. The type of thermal protection you wear largely depends on the water temperature. While every person varies in their needs for proper thermal protection, the general range for thermal protection while scuba diving is as follows:
>85 °F: Nothing-skin suit
73-84 °F: 2mm to 3mm
66-72 °F: 5mm
50-65 °F: 7mm
<50 °F: Drysuit
In addition to wetsuits, other thermal protection including hoods, gloves, and proper booties are essential to keep you warm.
Another condition that might limit how long you can SCUBA dive is the boat operator’s time limits. Sometimes, the divemaster will tell you how long you can SCUBA dive so that the boat can move on to the next dive site and keep on schedule. Additionally, weather and currents might change while you are diving, which may limit how long you can SCUBA dive as the divemaster may have to recall you from the dive for safety reasons.
How Long Can You SCUBA Dive in Age?
If you are reading this and thinking how long can you SCUBA dive as in age? This is really dependent on your overall health. Regular SCUBA dive physicals will help you and your doctor determine how long you can SCUBA dive. As of July 5, 2019, the world’s oldest SCUBA diver is 95 years old!
Overall, how long can you SCUBA dive depends on a few factors, but nitrogen absorption and air consumption are the two primary factors that limit the length of a SCUBA dive. As always, proper dive planning will allow for maximum dive time to see the best things at your current dive location. Just remember proper thermal protection!
*Also important to note, we strongly recommend the proper SCUBA certification and/or training before your first dive. Contact your local shop for more information on where to start!
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