Scuba Diving Information

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.

I didn't look into the truth of the statement, but my dive instructor said that it was mandatory to own a compass to become open-water certified. I was annoyed by this for two reasons: 1) compasses are expensive and 2) I knew that long before I did a dive where navigation by compass was necessary, I'd have a dive computer. I guess it's the cost of playing the scuba game.

When using a BC [buoyancy compensator] with an integrated weight system, is it better to put more weight in the upper back weight pockets? Especially for wreck diving where losing a front weight pouch that could cause a rapid ascent.

The abridge version of this article appeared in the October '95 issue of Sport Diver magazine.

We all remember those first dive classes when we were bombarded by new terms, complex charts, and the thought of coming face to face with dangerous sea creatures. But there is a whole list of terms that we were never taught but had to pick up on the back reefs of the world -- hushed definitions and observations whispered from diver to diver when the instructor isn't looking. I hope you enjoy my tongue in cheek reference to "proper" diving terminology.

There's already a lot to remember when scuba diving so it's no surprise that divers, especially new ones, struggle with navigating underwater without a compass i.e. natural navigation. Fortunately, natural navigation isn't all that difficult -- it merely requires knowing a few things to look for and paying attention to underwater cues.

Without special equipment you're not able to verbally communicate underwater. So it's a good thing that the various scuba organizations such as PADI have standardized hand signals for communication. Here are the basic ones (click on the image for a larger view):

Source: Pages 4 and 5 of Scuba BSA

One exercise that's required for scuba training is an emergency swimming ascent. I don't think that I'll be able to do that and here's why: My entire life, I've suffered with ear problems (infections as a kid and as an adult difficulty in equalizing during airline flights and driving in the mountains). It's not that I can't equalize, it's just that it takes a long time. My concern isn't really getting down; it's that if I have to make a continuous ascent, I won't be able to equalize. My buddy said that this is called a reverse block in diving lingo, and that I'd learn how to deal with it in training. I'm not so sure. Should I reconsider my decision to enroll in the class? Or, is there a way that I can opt out of this particular skill because of my condition?

Can a person who has had bypass surgery dive with restrictions?

The short answer is "possibly," and, of course, depends on individual circumstances. Certainly, many divers have had the procedure performed, and have been cleared for diving after this and other forms of heart surgery. That's probably not surprising given that surgeons perform these procedures by the hundreds every day to the tune of more than 500,000 times annually. Diving and other forms of strenuous exercise are possible after bypass surgery because, if the procedure is successful, the patient should become free of the symptoms of coronary artery disease, and the heart muscle should receive normal blood flow and oxygen.

Anyone who has traveled will be able to relate to at least a few of these...

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While scientists remain divided on the issue, experienced technical divers are adamant that divers can stave off some of the effects of narcosis by continued and frequent deep diving. This is probably due to both physiological adaptation, and because the seasoned diver develops coping skills, such as concentrating more intently on the task at hand. The adaptation is only temporary, however, and decays over a matter of days or weeks once diving ceases. The coping skills may last longer. A high motivation to complete the task appears to help reduce symptoms, as well.

Do I take my training here locally, and make my check-out dives in the murky cold water, or take my course while I'm on vacation somewhere warm? One friend told me that I could actually complete my classroom and pool training here, and do my open-water work someplace nice (read: warm). They're all encouraging me to take my training locally because they say I won't really be qualified to dive around here if I only have warm-water experience. Any advice?

We are usually instructed to look high and low for your buddy, spin in a 360-degree pattern and make absolutely sure they are nowhere in sight. Then, as a last result, return to the surface and hopefully you'll reunite. However, articles and the textbook instructions keep telling us to make a slow ascent to the surface to find them, but they never mention safety stops while completing this procedure.

It's a common misconception that hypothermia is an exclusive concern of those who dive in cold water. So, if you think tropical divers are immune to the problem, think again. There is, in fact, a well-documented phenomenon known as warm-water or silent hypothermia.

One of the most important aspects of safety in diving is that of personal health and fitness. We all know that we shouldn't dive with a cold or if we aren't "well," but remaining objective in the assessment of our personal fitness for diving can be a difficult task. It is very easy to rationalize away any number of contra-indications simply because we want to dive.

In divers, the effects of narcosis generally start with some form of impairment of mental function. This may include loss of memory, reasoning ability or a reduced ability to concentrate or to make sound judgments. These symptoms are especially dangerous because they often occur at times when divers need their wits about them the most; yet the individual may not even be aware that anything is wrong. As these symptoms can causes lapses in judgment, a "narked" diver can easily run out of air or overstay his allowable bottom time. It also makes a breakdown of the buddy system much more likely.

After getting my open water certification, I went diving in Belize where I did my first 9 dives including a night dive. I had a lot of fun overall, but not everything went as well as I thought. And I'm guessing the problems I had are pretty common with first time divers so I thought I'd share them.

If, after a dive and on your way onto the boat, you drop something in the water, is it safe to go back in to retrieve it assuming you have dive time left and air in your tank?

If you read the PADI Scuba Diving Instruction Manual or watch the DVD you may get the impression that the volume of air in a scuba tank decreases as you descend. I'm 99% sure this is wrong i.e. the volume of air doesn't change. I even asked about it during the in-person scuba classes, but the instructor, dive master, and the rest of the students agreed with the manual even though not one of them could explain how air in a rigid, sealed tank could be affected by outside air pressure.

The following lists the signs and symptoms of nitrogen narcosis at various depths.

Has your tank strap ever worked loose during a dive and allowed the scuba cylinder to move, or even slip completely out of the buoyancy compensator (BC) backpack? If not, you must be doing a good job of cinching the tank strap when mounting the BC. Mounting the BC so the cylinder stays put is a critical part of assembling a scuba unit

As a case of mild hypothermia can become moderate or even severe in a matter of minutes, the most important first aid measure when dealing with any suspected occurrence is preventing further heat loss. This means getting out of the water and restoring body heat.

I seem to have a problem with claustrophobia, but from past experience snorkeling I think I can deal with wearing a mask. What I don't think that I can deal with is wearing one of those thick rubber hoods. I've watched divers trying to deal with them, and it looks terrible, especially when wearing wet suit gloves. Watching one student who was fumbling with her hood, I even overheard the instructor say that hoods were hard to use and get used to, and made equalization difficult. I can't imagine how wearing a hood must feel underwater with all the pressure. I'm wondering do I really need to use a hood to dive locally if I limit my diving to summertime? Or, am I just making too big a deal out of this?

Being chewed up and spit out onto the beach by a thundering wall of turbid water is not what I call a fun dive outing. Entering and exiting through the surf zone can be a tricky and sometimes punishing scuba experience, but with training and the proper technique, anyone can determine if the surf is manageable and get through safely.

What is Visibility?

Visibility, quite simply, is the prevailing distance at which an object can be seen when looking horizontally underwater. Of course, there are factors that influence the visibility of an object underwater including its size, shape, and contrast against the background. And visibility is affected by light levels and depth so even really clear water will have poor visibility if the sky is cloudy and you're at 100 feet.

Under the right circumstance, the very air we breathe can actually kill us. Well, not the air so much as the oxygen component within it. If you're a seasoned diver, particularly if you hold a nitrox certification, you may already know that. But if you're new to diving, the fact that the gas we depend on to sustain life can, under the right conditions, become deadly poisonous may come as a real shocker.

Choosing the right buddy for a dive can be an important aspect to the enjoyment and safety of diving. By choosing a buddy who shares our ideals, goals and values, we are more likely to have a truly compatible buddy, and more likely to enjoy sharing a dive together. Pairing up with an underwater photographer could be great for a diver who likes to take it slow and draw in the details. On the other hand, for the type of diver who likes to cruise the reef, this might not be a good match.

While we call the condition nitrogen narcosis, almost any gas can have a narcotic effect when breathed under enough pressure. The condition produces a state like alcohol intoxication or breathing nitrous oxide ("laughing gas") at surface pressure. The good news is that, unlike decompression sickness, the effects of narcosis are completely resolved by ascending to a shallower depth, and with no long-term consequences. Therefore, provided a diver is aware of its symptoms and ascends to manage it, narcosis rarely develops into a serious problem.

Most divers are cautious and attentive in the way they prepare for and conduct themselves while diving. They know the rules and limits, they check their equipment over carefully, and they don't push the limits too far or too often. When it comes to injuries, we're probably more likely to get hurt playing softball or soccer than we are to suffer an injury on a dive. But when that unusual circumstance comes along, it's important to have a plan. After all, we can't stay underwater forever, and some problems need to be resolved pronto. We need to think about what could possibly go wrong on a dive, and have a plan for what to do if that "worst-case scenario" should arise.

To understand the current theory for what causes nitrogen narcosis, you must first know a bit about how the nervous system works. Electrical nerve impulses are transmitted throughout the body via nerve cells called neurons. These neurons, which are made partially of lipid (fat) tissue, transmit electrical signals to other neurons at junctions called synapses. The narcotic potency of an inert gas is a function of its solubility in fat tissue -- those that dissolve more easily into fat are more narcotic. The greater the solubility, the less partial pressure is needed to induce narcosis. Sedation occurs, it's thought, because the inert gas causes the synaptic membrane to expand, which slows or stops transmission of electrical impulses.

Scuba diving is pretty unique as far as a leisure activity goes, and for lots of reasons. Not the least of which is that it takes place in an environment completely foreign, and hostile, to human existence. It's also the only sport that I know of in which you literally have to pay for the air you breath. But perhaps the most unique aspect of diving is that even if we do everything right we can still fall victim to life threatening disorders. Furthermore, the deeper we go, the greater the risk we incur. This is in stark contrast to almost every other sport or recreational endeavor in which you'll normally have to do something wrong before you get into any kind of trouble. Not so for divers, though. We're exposed to hazards merely by being underwater.

While no one is immune to nitrogen narcosis, there are some things you can do that might reduce its effects. First, be very careful about exceeding depths deeper than you're used to unless you have advanced training or are under supervision of more experienced divers. Even if you're an experienced deep diver but haven't done it in a while, it's a good idea to work up to a deep dive by making a few progressively deeper "rehearsal dives." Be sure to practice the tasks you'll perform on the deep dive, too.

As we all know, lead is a neurotoxin for humans. Every time you dive with shot lead weights, you may see a cloud of dust falling from the lead weights, even if they are 3-4 years old and used hundreds of times. Some scuba stores with pools on site usually have weights in the pool area, and lead weights are used in the pool on a daily basis. With all this contact with lead, are scuba divers at risk of lead poisoning?