01.03 How can I make sure I snorkel and dive safely?

(approximately 5 minutes reading and 2 minutes doing the exercise)

Photo by Dan Gold on Unsplash

Snorkelling is an activity that involves floating along the surface of the water and occasionally diving down to look at something. When diving, the snorkel tube fills with water so you need to hold your breath. When you surface again, you can tilt your head back shortly before reaching the surface to encourage water to drain out and you can also expel the water with a sharp exhalation. Usually, snorkelers are in shallow reefs, less than 4 metres (approximately 13 feet) deep. Deeper reefs will require you to dive more often, which requires more fitness and skill. Due to the depths involved, the dangers are more from those around you on the surface in motorized crafts. Sun burn is often a problem as well.

Photo by Sebastian Pena Lambarri on Unsplash

Deep sea diving, also known as scuba diving, is any dive deeper than 18 meters (approximately 60 feet). As a recreational diver, you will be limited to 40 metres (approximately 132 feet).  Your first deep dive should be under the supervision of a dive instructor. You can do this during your Advanced Open Water Diver course. You will be trained to dive to a depth of 30 meters.

When you scuba dive with compressed air, the air you breathe will become denser as you go deeper due to increasing pressure.you take in extra oxygen and nitrogen. This means you consume more air while deep diving compared to shallow diving. Your body uses the oxygen, but the nitrogen is dissolved into your blood, where it remains during your dive. As you swim back toward the surface after a deep dive, the water pressure around you decreases. Decompression sickness, also called the bends, is caused by a rapid decrease in the pressure that surrounds you.

In order to avoid the bends, you must plan any scuba dive BEFORE diving. There are tables available to calculate and plan out a safe dive [web page]. The National Association of Underwater Instructors out of Florida has a set of rules to keep you safe. These include:

1. Ascend no faster than 9 meters per minute. This is 0.3 meters every two seconds. You need a timing device and a depth gauge (or a dive computer) to measure your rate of ascent. This rate will seem quite slow to you.
2. Use the deepest depth you reached during your dive to determine the dive schedule for your dive even if you spent little time at that depth and the majority of your dive at a shallower depth.
3. Always make your deepest dive first when making a series of dives. Plan each of your repetitive dives to a shallower depth than your previous dive. This might allow you to offgas nitrogen on progressively shallower dives and prevents you from carrying progressively larger amount of residual nitrogen on deeper repetitive dives.
4. Surface Interval Time (SIT) must be at least 10 minutes between dives. If your SIT is less than 10 minutes, you must consider your second dive as a continuation of the first dive. NAUI recommends a SIT of at least one hour between dives.
5. Always allow yourself enough time to make a slow, comfortable ascent with plenty of air.

If you plan the following dive, without referring to the tables, do you see any issues with the dive?

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