Positive Attitude

Positive Att.

The dive leader must recognize that his or her profession involves more than just diving. Every student and certified diver with whom the dive leader interacts is a customer; in this regard, a major responsibility of the dive leader is delivering customer service. Keeping this fact in mind will go a long way toward helping the dive leader set an appropriate tone for these interactions.

Obviously, the dive leader should be dependable and reliable. The dive leader should strive to perform each assigned task to the best of his or her ability. He or she should adhere to commitments, arrive on time for classes and dives, and be properly prepared. The dive leader should be appropriately attired for the customers with whom he or she will interact, and the circumstances in which this interaction will take place. The dive leader always should treat each individual with appropriate respect.

When approached by a student or certified diver with a question or problem, the dive leader should address the issue directly in a helpful manner, with sincere interest and concern for that individual. The discussion should focus on resolving the issue. When it is appropriate to explore the source or cause of a problem, such should be addressed in a factual manner without criticism, while also offering alternate or preventative measures that would preclude this problem in the future. At no time should a customer feel belittled or embarrassed.

At some point during training, it is not uncommon for a typical student to encounter difficulty in performing one or more required skills. When this occurs, the student might quickly become frustrated and begin to doubt his or her own abilities. Here it is important that the dive leader be both supportive and patient; any negative response will only further exacerbate the situation. Clearly this is not the first student who has ever encountered some difficulty, and it certainly won’t be the last. To bolster a student’s confidence, the dive leader first should focus upon the things that this student is doing correctly, and compliment the student accordingly. The dive leader next should identify the actual part of the skill that is causing the difficulty, again explain the proper technique in a thoughtful and step-by-step manner, and then help the student to work through the difficulty with repeated encouragement.

Finally, the dive leader also should be enthusiastic. It might be the tenth time in a row that a Divemaster is escorting a dive on the same site, but for the customer it might be the first visit. The visibility may have been better last week, but the customer is here now to dive. The same question already might have been asked a dozen times today by other individuals, but never before by this customer. The dive leader might actually prefer to be somewhere else, or doing anything other than this, but there is absolutely no reason for the customer to know it. To remain enthusiastic, the dive leader needs to remember that despite anything else that might have occurred, the priority now is to appropriately interact with this particular customer in a positive manner.


Role Model Behavior

When it comes to diving, the Divemaster and Assistant Instructor must recognize that they are being observed, almost constantly, by both students and certified divers. Whether intended or not, every action by the dive leader effectively becomes a demonstration of how things are done by a professional. The manner in which the dive leader prepares for a dive, conducts himself or herself in the water, and cares for his or her equipment, are all being noted. The dive leader’s own behavior sets the example, which then will be emulated by others.




Unfortunately, there is no universal norm for the compensation of dive leaders. In some cases the dive leader may be compensated through a salary or commission. Those working in resort areas might rely heavily upon customer gratuities as compensation. In other cases, especially for those dive leaders assisting part-time with classes at a local dive store, the compensation may be less tangible perks and other benefits. In any event, in recognition of the work performed as a professional, some form of compensation is appropriate.

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Chapter 3 Quiz

Diving Physics

Diving Physics: Part 1

Topics Covered in this Chapter:

  • Introduction
  • Physical Properties of Water
    • Density of Water
    • Refraction of Light in Water
    • Diffraction of Light in Water
    • Color Loss in Water
    • Transmission of Sound in Water
    • Thermal Conductivity of Water
  • Review Questions


Diving Physics

A general understanding of physics is a key component in the overall body of knowledge that is expected of a dive professional. The laws of physics are equally applicable both above and below the water’s surface. In general, people have learned to recognize and accept many of these principles in their daily non-diving activities, often without giving them much thought. But then again some things don’t change a lot at the surface, and sometimes a person can be led to mistakenly believe that’s just the way it always is. This may help explain why a new diver is often surprised, and perhaps a bit perplexed, when suddenly discovering that things can be very different underwater.

To alleviate confusion, every new diver is introduced to an appropriate amount of physics during the Open Water Diver Course. Naturally, at that level the information an individual needs is fairly basic. Additional information is then addressed as it becomes relevant during subsequent training. Accordingly the reader likely will have at least some familiarity with many of the principles presented here. Undoubtedly, however, some of this material also will be brand new. The extent of knowledge appropriate for an individual at the leadership level is now quite comprehensive.

The information addressed in this chapter will help the reader develop a thorough understanding of the impact of physics upon diving. Of course any discussion of physics also includes some math. In essence, physics is the science of quantified and predictable cause-and-effect relationships.

Armed with this new-found knowledge, it certainly is not suggested that a new dive leader attempt to convey this information to every student with whom he or she now comes into contact. Instead the sharing of one’s knowledge should be tailored according to the recipient’s level of training. Any additional information should be reserved for that individual who expresses further interest.

NOTE: For your convenience, we have compiled a PDF containing the Mathematical Equations Found in this section. Please CLICK HERE to download the SDI/TDI Gas Laws Worksheet. Internet Explorer users: to save the file right click on the link and choose “Save Target As…”

Principles of Pressure

Gauge Pressure

Another term with which the reader should be familiar is gauge pressure. Gauge pressure refers to the manner in which a diver’s instruments measure and display certain types of pressure-related information. Gauge pressure disregards atmospheric pressure, and only provides a measurement of the actual force being exerted by another source of pressure.

Gauge pressure is employed in two types of instruments used in diving. The first is the diver’s submersible pressure gauge, or air-integrated dive computer, which measures and displays the internal gas pressure within a scuba cylinder. This information normally is displayed in terms of bar, or in terms of pounds per square inch (abbreviated as “psi”). Normally a diver will select and use an SPG that displays cylinder pressure in the format with which he is most familiar; on occasion, however, the divemaster may be approached by a perplexed diver who is seeking assistance in interpreting the information displayed by an SPG. Remember that 1 bar equals 1 atm, and that 1 atm also equals 14.7 psi. To convert an SPG reading from bar to psi, or from psi to bar, the divemaster may employ the following formulas:

Imperial-to-Metric: bar = psi / 14.7

Metric-to-Imperial: psi = bar x 14.7

Because gauge pressure effectively disregards atmospheric pressure, it must be recognized that when an SPG reads zero, the scuba cylinder is not actually empty; instead it still contains air under 1 bar or 14.7 psi of pressure.

The second type of instrument employing gauge pressure is the diver’s depth gauge or personal dive computer. This type of device measures the ambient pressure being exerted upon the instrument itself, effectively disregards the atmospheric pressure, and indicates only that portion of the ambient pressure that is attributable to the weight of overhead water. Typically this information is displayed in terms of either meters or feet of depth in seawater. Again, to assist a perplexed diver, the divemaster may need to translate these values. To convert a depth gauge reading from meters to feet, or from feet to meters, the reader may employ the following formulas:

Imperial-to-Metric: meters = feet / 3.3

Metric-to-Imperial: feet = meters x 3.3

Again, the depth gauge or personal dive computer disregards ambient pressure and displays only water pressure. In terms of practical use while diving, gauge pressure is quite effective in identifying depth for the diver. However, as will be demonstrated in subsequent sections of this text, whenever evaluating the effects of pressure the diver always must consider the ambient (total) pressure. The mathematical calculations described immediately below will assist the reader in readily converting depth to ambient pressure, and ambient pressure to depth.

Principles of Pressure

Depth-to-Pressure Calculations

The following abbreviations appear within the formulas in this section:

  • “P” for pressure
  • “D” for depth

It is a fairly straightforward process to convert depth (gauge pressure) to ambient pressure, provided that the reader remembers to account for both the weight of the overhead atmosphere and the weight of the overhead water. As noted above, 10 meters of seawater equals 1 bar, and 33 feet of seawater equals 1 atm. The appropriate mathematical formulas are depicted below:

P = [ D / 10 ] + 1 or P = [ D + 10 ] / 10
Example: What is the ambient pressure at a depth of 14 meters in seawater?
Answer: 2.4 bar: [ 14 / 10 ] + 1 = 2.4 bar or [ 14 + 10 ] / 10 = 2.4 bar
P = [ D / 33 ] + 1 or P = [ D + 33 ] / 33
Example: What is the ambient pressure at a depth of 46 feet in seawater?
Answer: 2.39 atm: [ 46 / 33 ] + 1 = 2.39 atm or [ 46 + 33 ] / 33 = 2.39 atm
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Chapter 7 Quiz

Principles of Pressure

Ambient Pressure

Scientists often refer to the total force being exerted simultaneously by all existing sources of pressure as absolute pressure; in diving it is more commonly referred to as ambient pressure.

Ambient Pressure

The first source of pressure affecting all things on Earth is the weight of the overhead atmosphere pressing downward. Of course this force will vary somewhat with altitude, as a person standing on top of a mountain will be subjected to less overhead atmosphere (and thus less pressure) than a person at sea level. This force also varies slightly with changing weather patterns. However for practical purposes, at or near sea level (up to an altitude of about 300 meters or 1000 feet above sea level) atmospheric pressure may be considered to be a constant. Importantly, while at the surface, the weight of the overhead atmosphere normally is the sole source of ambient pressure.

In the metric system the weight of the overhead atmosphere at sea level is defined as one barometric unit of measure, commonly abbreviated as 1 bar; it is equivalent to one kilogram per square centimeter. In the imperial system this weight is defined as one atmosphere, commonly abbreviated as 1 atm; it is equivalent to 14.7 pounds per square inch. Consequently, 1 bar is equivalent to 1 atm. Some of the equivalent values cited here might differ slightly from those appearing in other reference materials but for practical purposes, within the context of diving, any such difference is negligible.

Once a person, object or gas is taken below the surface of the water, the added weight of the overhead water becomes a second source of pressure. As depth increases, pressure also increases because of the additional weight of overhead water pressing downward. Pressure increases by 1 bar or 1 atm for every 10 meters or 33 feet of depth in seawater. The ambient pressure exerted upon a diver now will be equal to the weight of the overhead atmosphere plus the weight of the overhead water.

The following table effectively demonstrates the relationship between depth and ambient pressure:

Depth in SeawaterAmbient Pressure
0 m
0 ft
1 bar/atm
10 m
33 ft
2 bar/atm
20 m
66 ft
3 bar/atm
30 m
99 ft
4 bar/atm
40 m
132 ft
5 bar/atm
50 m
165 ft
6 bar/atm