I'm curious as to what agency sets depth limits on solo diving and uses that rule. And is it on their cards? My SDI solo instructor said nothing about that. And though I have yet to do any meg tooth dives so far I would expect them to be conducted as same ocean buddy or solo dives given the environment and techniques required. No need for a solo cert or training. Just common sense. Anyone doing 100+ ft dives in the atlantic should be capable of doing those dives alone. Proper equipment yes. But that would be up to the individual diver to decide what is proper for them.
Jim,
To answer your question... I can not find any reference to this in the current SDI manual or Instructor materials. To be honest, I'm not sure if it is or ever was an official standard, however I began teaching solo diving a few years back when all agencies accept SDI frowned upon it. Some of the more recognized names in the sport recommended this as a limit (see article below.) The limit made perfect sense and I adopted it as a standard in my teaching. As I said, I can not find it in my new SDI materials... but I'm almost certain it was in my old materials. I could however be wrong... and it may have been something I adopted based on the below article. On the SDI diver submission form (sent in to get the c-card) in the lower left corner there is a spot for the Instructor to fill out the depth to which the diver is certified in the specific specialty. I have always required divers as part of their training to conduct a free dive and measured the max depth they reach (while I'm on Scuba.) I then 2X this depth and list it on their submission form. Because I have had cards mailed directly to the students, I have not seen whether this is listed on their card or not. That is a good question. I may call one of my students today to find out. If this is not a standard, it clearly should be. It makes perfect sense.
As someone else noted in this thread, in a perfect scenario, with a full breath of air, it is quite possible for someone to ascend from 100 ft on a single breath - exhaling tiny bubbles are the way to the surface... but while it is possible - rarely is the circumstance perfect enough to allow for this. By limiting depth to 2X a free dive, the likelihood of such an ascent being successful - doubles. Just my two cents. I placed the specific reference paragraph in BOLD below.
Excerpt - Copied as written and found on the internet -
The Buddy System Reexamined
By Alex Brylske. Reprinted from Dive Training, Sept. 1996
These situations all point out that at some time all of us end up solo diving whether we realize it or not. So, the key to safety is not in who or how many other divers accompany you, but in self-reliance. Only when you can take care of yourself can you truly be prepared to help someone else.
Achieving Self-reliance
Because of both its practical and psychological benefits, self-reliance should be a prerequisite for all divers - even those who would never consider entering the water alone. From the practical standpoint, a self-reliant diver is one who can handle problems even if a buddy is not around or paying attention. To a self-reliant diver a buddy is an aid, not a necessity.
From a psychological perspective, a self-reliant diver is a self-confident diver who knows-buddy or no buddy-he or she can handle whatever problems might arise. This translates into less apprehension and anxiety. The benefits are a reduced breathing rate, lower threshold of panic, and improved ability to pay attention to the dive and to his or her buddy.
Achieving self-reliance requires three essential conditions. The first and most obvious is that you possess skill competence. At minimum, you must be able to perform all the skills you learned in your entry-level course in a calm, deliberate manner and without the need for assistance. You should be able to do this in an environment typical of the conditions you normally encounter.
Skill competence also implies some familiarity with self-rescue and the ability to offer assistance to others. The willingness to help your buddy is meaningless if you don't know how to do it. But such knowledge and skill do not just materialize out of thin air. To gain these insights requires training, such as a diver rescue course.
The second element of self-reliance is that you maintain an adequate physical condition. The question is, what's adequate? That answer is highly personal and varies according to circumstance. Start by reviewing the kinds of environmental conditions you usually encounter. Do you normally dive in heavy or moderate currents or surf? At what depths and temperatures? you dive in open ocean or in a lake or quarry? Can these conditions change from day to day, or even hour to hour?
Your physical condition must match or, better yet, exceed the conditions you dive most often. What this means, of course, is that divers who dive primarily on the shipwrecks off the northeastern U.S. need more physical stamina than those who confine their diving to summertime excursions on picture-perfect days in the Florida Keys.
Third, and perhaps most important, self-reliant divers understand and accept their limitations. This may be the most difficult element to achieve because it requires a great deal of a quality many of us lack-self-honesty. We all have an internal vision of ourselves, and sometimes that vision belies reality. For divers whose self-image is overblown, the result can be downright dangerous. Truly self-reliant divers understand their strengths and limitations, and as a result, when they decide to dive, it's with a high level of psychological and emotional confidence. This is the final measure of a self-reliant diver.
The Decision to Solo
So far, we have based our discussion on the assumption that any breakdown of the buddy system's effectiveness is unintended and requires corrective action. This ignores an entire segment of divers who take a completely different approach to the issue of personal safety-those who intentionally dive without a buddy.
Although a comparatively small segment of the diving community, these revisionists contend that placing your faith in a system that's dependent on someone other than yourself is misguided. So, they conclude, better to rely only on yourself because you are, after all, the only person you can absolutely count on in the event of an emergency.
Furthermore, many solo divers contend that there are other reasons to abandon the idea of a buddy. They maintain that some diving activities, in fact, lend themselves to diving alone. For example, the last thing an underwater photographer wants is someone scaring the marine life, destroying visibility, or getting in the way of the picture. Indeed, many professional underwater photographers dive alone unless they need a model. Even in those situations where the photographer is accompanied, for a Practical Purposes the photographer is solo diving-his or her attention is devoted completely to getting pictures, not watching another diver.
Like photographers, some underwater hunters often Prefer to go it alone. Many lobster divers look at buddies as nothing more than Competitors for a limited resource. Having a buddy means that they will give away the location of their special spots and successful techniques. Spearfishermen sometimes feel the same way about buddies. Furthermore, they add, diving without a buddy is safer because in limited visibility a partner risks becoming an accidental target.
Another reason some choose to dive alone is simply because they don't want to be responsible for someone else. Ironically, many consider anyone who would dive solo as irresponsible, but devoted solo divers are often more responsible than buddy divers. That should not come as a surprise because a lot of careful consideration, planning, and self-reliance is essential to becoming a proficient solo diver. Many divers choose to dive alone even when others are willing to accompany them. They believe that diving alone is better than diving with someone they don't know, Of who is incompetent, inexperienced, unprepared, or unwilling to act as a true buddy. Frankly, that's difficult logic to counter. Ron Von Maier, author of Solo Diving:
The Art of Underwater Self-Sufficiency, Sums it up perfectly: "Any buddy is not better than no buddy."
Another big reason some divers go Solo is purely one of Practicality- they just have no one else with whom to dive. We often forget that diving is not a popular activity everywhere, and not being able to find a buddy can be a serious impediment. This is not a minor issue. One of the primary factors the diving industry points to in explaining why people drop out of diving is simply that they cannot find someone with whom to dive. While endorsing the Practice of solo diving for that reason is difficult, it's also difficult to rebuke those who do.
The final reason for going it alone may be the most compelling-the solitude. While there's certainly something to be said for sharing the experience, solo divers often feel that diving is best appreciated in complete isolation from others.
The underwater realm is, after all, a silent world; and some feel that the accompaniment of another diver is an intrusion.
The Solo Recipe
Solo diving is often misinterpreted to mean nothing more than jumping in the water without a buddy. That's not solo diving; that's just plain stupid diving. Because they have no one else to fall back on in case of a problem, responsible solo divers follow a planning routine that is often more rigorous than most buddy divers. In addition to the standard pre dive preparation, they follow a set of special rules and safety considerations.
Perhaps the most important rule for solo diving is that the diver has past experience in similar diving conditions. In other words, the dive is not beyond the diver's level of experience and personal comfort zone. This applies not only to the conditions present at the time the diver enters the water, but also to how those conditions might change during the course of the dive. It's one thing to enter the water on a bright calm day with no current, but if the weather or tide changes, no one will be around to help.
If in the planning process a solo diver determines that he or she can handle the dive only if conditions remain stable, then that's a good indication to abandon the solo plan and make the dive with an experienced buddy. This is an excellent illustration of the need for self-honesty mentioned previously.
Once in the water, perhaps the most important consideration for solo diving is air management. Some suggest that solo divers take the time to meticulously calculate air requirements and probable air usage. Except for mission oriented technical dives, however, divers rarely are willing to do this. A simpler and more practical planning guideline is to use the "rule of thirds." This simple rule says that you should plan to use only one-third of your air supply for the trip out, then another third for the trip back. The final third is a reserve for unforeseen circumstances, which, when diving without a buddy, can be a particularly vital consideration.
Another air management guideline is to calculate your returning air pressure in consideration of your depth. To do this, round off your actual depth to the next greater increment of ten, then add a zero to that figure. The result is the air pressure at which you should begin your ascent. For example, assume you are making a dive to 57 feet (17m). Round that up to 60 (18m) and add a zero. You should then begin your ascent when you reach an air pressure of 600 psi.
What if you screw up your air management plan and run out of air? No one, of course, will be around to give you an octopus or alternate inflation regulator (although a solo diver should still carry such a device if, for no other reason, a first-stage malfunction occurs). The only out-of-air contingency that will work for a solo diver is a completely redundant air supply, such as a Spare Air' or pony bottle. When a solo diver is making deeper dives, larger capacity pony bottles or dual tanks with independent valves or separate regulators are essential.
Von Maier, one of the few people who has written extensively about the subject, advocates two other commonsense rules for solo diving. The first is that you should never solo dive deeper than twice the depth to which you can free dive. This tends to impose a reasonable and personalized depth limit.As few people do much free diving anymore, some might not see this as a usable guideline. Instead, you might limit a solo dive to a depth no greater than that from which you have performed a controlled emergency swimming ascent. That way you have the self confidence of knowing that even without air you can make it to the surface because you have done it before.
Von Maier's second rule is another sensible one: Your underwater distance from your exit point should not exceed the distance you can comfortably swim in full scuba gear while at the surface. Remember, getting to the surface is only half the battle. You also have to get out of the water, and there won't be anybody to help you.
