5 Questions Every Scuba Diver Should Answer
Table of Contents
1. Visibility limits. How much is enough?
When it comes to setting visibility limits, training and experience are generally the two primary factors in the equation. If our diving has primarily been in clear water, our comfort level with limited visibility may be decidedly low.
Consider other environmental factors as well when making the determination. For example, are there currents? Combining currents and poor visibility can seriously challenge our navigation skills, to say nothing of the psychological effects.
Consider entanglement hazards. When we combine currents and entanglement hazards, we need to give ourselves a greater margin of safety.
Finally, consider the depth when deciding on visibility limits.
2. Depth limits. How deep will I go?
Depth limits are fundamental to any dive, and a variety of factors can influence the personal limit we set First, we should never dive deeper than our training or level of certification dictates, but other factors are critical as well. While we may have experience and a high comfort level diving to 80 feet in clear, warm water, the same depth in cold, dark waters can have us riding the ragged edge. To dive safely in reduced or poor visibility may require additional training or experience.
In fact, a variety of factors can and should influence our personal depth limits. Breathing gas obviously is a factor in determining our depth limits for a particular dive. Every breathing gas, from air to the various nitrox blends, to trimix, carries with it a depth limit that we must observe. Remember, too, that deeper water usually means colder temperatures, so unless we have the proper thermal protection, we may want to limit our depth to maintain our thermal comfort. As our diving takes us to deeper depths, we rely on additional equipment to enhance our safety. At deeper depths we should consider the need for items such as a redundant air system, dive lights and surface marker buoys.
Finally, air supply (reserve air limits) and depth are closely related. Resolving a problem at a greater depth carries with it the need for more reserve air, so unless we're equipped with sufficient breathing gas, we may want to limit our depth as well
3. Reserve-air limits. How much reserve air is enough?
Divers often pick a convenient number to use as a limit for air reserve without really giving it adequate analysis, but air reserve limits are a key consideration. On a shallow dive in prime conditions (i.e., a low-risk environment), a limit of 500 psi might be acceptable. On the other hand, cave divers use the rule of thirds: one-third for the way in, one-third for the way back, and one-third as an emergency reserve. Usually, a limit that lies between these two will be appropriate for our dive.
Some factors to consider when setting a reserve-air limit are the depth, visibility, surface conditions, type of dive and the buddy we're diving with. Obviously, the deeper we are, the more reserve air we need to resolve problems and return to the surface. As we pass 33 feet, our air consumption is double that on the surface. At 66 feet, we have tripled our air consumption As visibility diminishes, the odds of a buddy separation or navigational problem become arguably greater, so we might want to up the reserve-air limit. Likewise, when surface conditions are demanding, we might be wise to increase our reserve-air limits to ensure that we have adequate air to reach the boat or exit point without surfacing.
The buddy with whom we're diving is another important factor in establishing a reserve-air limit. Let's say that a slight female and a large male buddy up for a dive. Due to her size and breathing rate, the female carries a 40-cubic-foot air cylinder. The male diver sports an 80-cubic-foot cylinder, and on a typical dive, they reach the 500 psi mark at the same time. While this may appear to be a good match, when we examine the situation at depth, the mismatch becomes obvious.
Should the female diver suddenly experience a problem that requires her to receive air from her buddy, the 500 psi remaining in the 80-cubic-foot cylinder might be adequate. However, if it's the male diver who suffers the problem, the 500 psi remaining in the 40-cubic-foot cylinder may be woefully inadequate due to the combined breathing rate of the two divers.
There are several ways to compensate for such mismatched dive buddies. One is to up the reserve limit for the diver with the smaller air supply. Instead of using 500 psi as the limit, choose 800 or 1,000 psi. Another option is for the diver with the higher breathing rate to carry a redundant air source, such as a pony bottle or spare air, to provide the extra air needed for an abnormal situation.
4. Buddy proximity. How close should we be?
This is a key question that many divers ask, and that some divers forget to ask. The idea of the buddy system is to have another diver by our side to assist in the event that something goes wrong. Remember, the timer is running down there, and if a diver experiences a problem with his air supply or regulator, or becomes entangled or ill, there may not be a lot of time to resolve the situation. While some divers are comfortable as long as they can see their buddy, in conditions such as reduced visibility it may be best to remain within touching distance. One way to answer the question for yourself is to ask what you would do if suddenly you couldn't breathe or became entangled. Carrying equipment such as a redundant air supply and emergency surface marker might influence your personal limit on buddy proximity.
5. Safety stop limits. Will I complete my safety stop solo?
Even for buddies who normally stick together, one place where the buddy system can sometimes come unglued is at the safety stop. Divers often consider the dive “over” once they reach the safety stop, and will surface separately after each one meets his or her personal stop obligations. While it might seem that the risks are minimal while dangling on a downline in 15 feet of water, we aren't completely out of the danger zone until safely on shore on board the dive boat. This is a subtle point or limit that dive buddies should agree upon.
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