Disclaimer
The comments in this article are specific to U.S. recreational diving. Other countries quite likely have different rules or customs. None of this information is guaranteed, but it is accurate to the best of my knowledge at the time this article was written. Use (or misuse) of this information is entirely the responsibility of the reader. Just remember, in the end, Darwin always wins.
What is it?
First of all, there are no government regulations with regard to recreational diving. Commercial diving has various regulations (OSHA and such), but recreational diving is a "self-regulated" activity. What this means is that the government has (so far) not decided that they should impose their bureaucracy upon the diving industry. There are no government regulations requiring a diver to be certified. There is no government required training criteria. Our C-cards are not a "license", they are just a piece of paper or plastic that states that we have met a minimum level of competency for the curiculum of a particular agency.
There are quite a few different certification agencies (PADI, SSI, YMCA, etc) and they each have similar curiculums. Most people agree that the instructor is more important than his agency affiliation. Some instructors are even affiliated with multiple agencies.
The main thing that certification (i.e a C-card) does for you is allow you to more easily get air fills for your tanks. There are no government regulations stating that they cannot fill your tanks if you don't have a C-card, but the various agencies and shops have instituted this policy. Some might question whether such a policy was actually legal, but there are ways around it if you are somewhat creative.
Frankly, diving is a fairly easy sport to learn. Some people take classes for a few weeks, some take weekend courses, and some take video courses. Each of these teaching methods would require the student to spend some time with the instructor for pool training and then two days of checkout dives at the end of the course.
Ways around it
So, you might wonder, if it is so easy, why do we need certification at all? Many of us who started diving many years ago taught ourselves how to dive. The most important thing is to be comfortable with your equipment -- panic kills. One other important thing to remember is to never hold your breath. I managed to teach myself how to dive and dove for quite awhile before I found out about this rule -- I guess it's a good thing that holding my breath never occurred to me.
My own technique for teaching myself how to dive was to get familiar with the gear on the surface and then move to a small lake for further learning. I started out on a boat dock and climbed down the ladder into the water. I stayed on the ladder as I submerged and got comfortable with breathing while underwater. From there, I moved towards longer trips away from the ladder and eventually better buoyancy control. This was back in the days when SPGs and depth gauges were luxuries. When the tank started getting difficult to breathe from, it was time to change the valve position on the tank's J-valve and surface. For these types of dives with only a single tank and one dive per day, having a decompression table was not even necessary since it was unlikey that you would be able to stay down long enough that you would have to worry about decompression.
What this boils down to is that it is entirely possible for you to teach yourself how to dive. Agencies are not necessarily required, although some people learn better in a structured environment.
Acquiring Gear
Although it is quite possible for you to be able to teach yourself how to dive, you need to have some gear to be able to do it. In fact, gear acquisition is probably the easiest part of diving. It has been my experience that no shop ever checks to see if you are certified prior to selling you gear. It is also possible to purchase the gear via mail-order or online via the internet. The problem comes with getting air fills. The shops tend to want to see your C-card before they will fill your tanks. Back in the good-old-days, you could likely skate by, saying that you left your C-card at home or if you were a regular customer of the shop, but these days, it's getting a lot more difficult.
If you know what to look for, you can often aquire good gear at an acceptable price on eBay. If you are new to the sport, perhaps it would be best if you were to get the advise from a friend who has more experience. I would strongly suggest that you stay away from the typical jacket style buoyancy compensator (BC) and go the backplate and wings style. If you put the gear together yourself, it's not all that more expensive than a jacket style BC and it provides considerably more flexibility.
Getting Air Fills
If you aren't certified, getting air fills can sometimes be challenging. Because of liability concerns, shops are considerably more hesitant to fill tanks if you don't have a C-card than they were 20 years ago. It's still possible though if you are a bit creative.
One of the easiest ways is to just have a friend who is certified get your tanks filled for you. Good friends will provide you with all the tools you might need to kill yourself -- great friends will even help you do it.
You can buy your own air compressor. Unfortunately, this can cost a couple thousand dollars, so unless you plan on doing a lot of diving, this option is definitely not economically practical.
Some of the fire extinguisher shops provide air for the firefighter SCBA tanks. I have encountered such shops that will fill my SCUBA tanks and they do not check to see if you have a C-card. An added plus is that they also did not check to see if the tank had a current visual inspection. These shops are also the ones who will do the hydrostatic test on your tank every five years. If you take it to your local dive shop, they just end up taking it to one of the fire extinguisher shops. As you can probably guess, taking it directly to the fire extinguisher shop will save you a few bucks.
Learning How To Dive
There are really two stages in becoming a diver -- learning how to dive and getting certified. Most people these days go to their local dive shop (LDS), sign up for the course, and get whatever certification that the LDS offers. Many of us back in the old days taught ourselves how to dive and went many years before breaking down and finally getting certified. Considering the fact that the various certification agencies allow kids as young as 12 to get certified, it is not unreasonable to assume that an adult of even just average intelligence should be able to teach themselves how to dive. There is information available on the internet and probably at your local library that would allow you to gain the basic knowledge that you might want to have before you get in the water with your gear. If you are moderately intelligent, you can probably even manage to figure it out for yourself without any books, just like we did long ago.
If you decide that you want to teach yourself how to dive, the first thing that you need to do is to get thoroughly familiar with your gear, it is a lot easier to catch your mistakes when you are on dry land than it is when you are in the water. One of the more common things that I've noticed people having problems with when learning to dive is just the concept of breathing while underwater. They have become so conditioned to the concept of holding their breath while underwater that the concept of breathing while underwater is sometimes a major hurdle for them to overcome. Just being comfortable in the water is a major part of learning how to dive. If you grew up in an area where you often spent time in the water, either snorkeling or just breath-hold diving to examine items on the bottom, you've got a good start on this since you comfort level of being submerged is higher than someone who has never spent much time in the water.
After you are thoroughly familiar with you gear, it is time to start using the gear in the water. You should use your mask during this process, but your fins tend to be optional, dependent upon the body of water that you are entering. I would not normally suggest a shore entry due to the uncontrolled nature of it if the bottom is uneven. You really don't want to fall while wearing your gear before you have gotten comfortable with it. As such, I would suggest either the shallow end of a swimming pool or a boat dock on a calm lake where there is a ladder leading from the boat dock down into the water. With the shallow end of the swimming pool, you start out with submerging your head while standing on the bottom. As you get more comfortable with breathing while your head is submerged, you will find that you can start moving around the bottom a bit. Once you are comfortable with this, you can put your fins on and move around the bottom even more. The main things to remember are to not hold your breath and to stay calm. If you are using a boat dock as your entry point into a lake, you should maintain a grip upon the ladder and climb down it until you are submerged. Do not relinquish your grip on the ladder. Once you are comfortable with breathing while your head is submerged, you can climb further down the ladder until you are a few feet below the surface. With most lakes, the visibility is such that you are not going to be seeing all that far, so you should maintain contact with the ladder. As you build confidence, you can move around the ladder and down to the point where only your hands have contact on the bottom rung of the ladder. You will discover rather quickly that you will need to learn how to equalize the pressure in your ears if you are going much below the surface. If you wait until you have pain in your ears, you have waited too long -- you need to come back up a bit and equalize. Once you have gotten comfortable with diving while maintaining contact with the ladder, you can add fins to your gear complement and this will allow you to move about further from it. If at some point you lose sight of the ladder, do not panic. You will need to surface and get your bearings. Since you are doing this at a boat dock, it is advisable that you do not surface in the path of a boat. Although a dive flag on a float is the proper way to deter boats from hitting you, if you are careful and understand what the boats sound like while you are underwater, you can surface in comparative safety even without one. It is possible that you might surface underneath the boat dock. If this happens, remember to remain calm. if it is a floating type dock, you will probably realize that you surfaced under the dock when you head hits the bottom of one of the floats. As such, there is a definite advantage in surfacing very slowly. If you find that you are under the dock, submerge a couple of feet and swim in some direction. If you notice the water getting shallower as you swim, it probably means that you are swimming towards shore while still under the dock and depending upon the design of the dock, this might not be a good thing. If this occurs, you might want to consider swimming 90 degrees to your current course or even back the way you came. It is going to depend upon how the dock is laid out -- you are going to want to swim to the closest clear area. Often floating docks are made up of floating sections with gaps between them. As such, it is often possible to get within one of the gaps and you'll be able to see where the closest clear area is located. When I taught myself how to dive, the dock was perhaps 12'x12', so finding the closest clear area if I attempted to surface while under the dock was not that difficult. One of the problems with long docks is that there are probably a lot of boats around that area -- otherwise, they wouldn't have the need for the long dock. As such, a long dock would not be my first choice when teaching myself how to dive via this method.
Once you've gotten comfortable with the use of your gear while underwater, the next step is to fine tune your diving skills, paying particular attention to buoyancy control. Ideally, you would want to be able to maintain the same position in the water column without the use of your fins. In my opinion, being slightly negative is better than being overly positively buoyant. If you are slightly negatively buoyant, all it takes is a kick or two to keep you at your desired depth. If you are overly positively buoyant, you will be constantly fighting to stay down and as such you will be using air at a higher rate. You do not want to be so negatively buoyant that you sink like a rock though. Since there is the chance that you might overweight yourself during your learning phase, it is advisable for you to practice in an area where the water is not so deep that sinking to the bottom might cause other complications (e.g. narcosis, increase air consumption, etc). If you are close to shore and somehow made the mistake of being massively negatively buoyant, at the worst you would just need to swim / crawl back upslope to the shore.
To become a good diver, it takes a bit more than this, but this will allow you to get to the point where you can start perfecting your skills. From here, you can start working on buoyancy control, proper weighting for your desired thermal protection, air consumption, etc. As a pilot, we consider our license just a license to learn -- even with a formal certification from a certification agency, it's not the different. Well, other than the fact that you can kill yourself a lot quicker if you don't do something right in an aircraft.
Conclusion
Although it is possible to teach yourself how to dive and go for many years without being certified, the cost of certification these days is such that it's not really worth the hassle. Even after 20+ years of diving without being certified, I finally broke down and got rubber stamped for a C-card. If you go with the class teaching method which lasts a few weeks, you can be certified for around $100 for the course and then whatever costs for the equipment rental, air fills, or site entrance fees on the days of the checkout dives. The thing to remember though is that just because you are certified, it doesn't mean that you are competent to do every sort of dive. It's a piece of paper or plastic that will allow you to gain more experience and learn though.
