A few years ago I was kayaking in the north end of Lake Natoma, a small lake in Sacramento. Folsom dam releases water a couple of miles up from the put-in that flows through a canyon with some very steep walled sections. Since they release water from the bottom of Folsom Lake,it is very cold in this canyon. It was warm and sunny when I launched and headed up the canyon. A large release from the dam was causing
strong currents.

 As I made my way up I came across a group of 4 paddlers in recreational boats. Like me, they were eddy hopping up through the canyon. I said “hi” as I passed by, they looked like they were having fun but were coming into an area where the current increased. As I went around the next corner I found a nice rock with a surfable wave on it and stopped to play around for a while. Then I realized that the group of 4 hadn’t arrived yet and decided to take a peek back around the corner. What I saw was a boat with no one in it floating down the middle of the river about a 100 yards away. The boater of a second kayak was paddling around it without saying a word. I decided to paddle back and see what was going on. As I rounded the corner I saw two of the boaters sitting in an eddy, I asked if everything was all right and they replied “yes, everything is fine.” Not believing them I continued back down river where, around the next corner, I found the missing kayaker holding himself pinned up against a sheer rock wall almost chest deep and no place for him to exit the water. He was shivering in his shorts and t-shirt. I had him climb onto my back deck and paddled him down river where I was able to get him back into his boat. This could have turned out pretty bad if he was in the water for much longer.

A basic class would cover all of this and make everyone much safer on the water–likely preventing this from getting as far as it did. It would have taught them how to get their friend back into the boat on the water, how to tow the boat over to their friend instead of just watching it drift down the river, how to signal someone for help, and a little bit about hypothermia and what will happen if they just leave there friend sitting in very cold water. It may have even taught them the paddling skills to prevent the wet exit in the first place… 
 The Foundation,
 When you build a tall building, if you just set it on the ground it will still stand. But when a storm kicks up, you will want one that was built with a strong foundation. So, in construction we have professional architects and engineers that design a solid building from the ground up. Sure, you and your buddy can fumble through it and build the building on your own. But it will probably take longer and wobble a little more than if you had paid a professional who has been doing it for years and knows the best way to proceed from the ground up.  
Which brings us to kayaking. When I started paddling, I started with a basic day-long sea kayak class at California Canoe & Kayak (where I now teach) and then went out and practiced on my own. Then, I took the next level class, which reviewed the prior taught skills and built upon them. For example, in the second class I learned what edging was, the how, and why we use it (and I still to this day use these skills). I benefited from the time the school spent over the years determining the best way to teach the skills progression. My buddy could have showed me this, but it would not have provided me the foundation and progression to let me really learn it.
The type of class you want varies by the type of paddling you will be doing. For flat water kayaking, the initial focus is on basic strokes and rescues. For white water, rolling is considered an essential skill, and thus is taught relatively early on.
 Never Stop Learning,
 There are classes for all levels of paddlers. Just because you paddle well doesn’t mean you know it all. I am a certified instructor who is comfortable paddling in all sorts of conditions in the bay and on the open coast, but there is still much for me to learn.
 One day on a coastal paddle I initiated for our club, we had an incident where someone came out of his boat in a very nasty spot in the rocks. After about 20 minutes of solid efforts from the group, the paddler was rescued. Afterwards, I felt I needed to be more prepared if something like this happened again, so, together with a few other solid paddlers, we contacted Roger Schumann who developed and taught a white water rock garden rescue class for us. He set it up and we spent a whole day on the coast doing actual rescues in conditions that were challenging just to paddle in. Many of the local shops have advanced classes for all types of kayaking. Some are regularly scheduled, and some are special classes where the school brings in a renowned expert from outside our area to teach. And there are also symposiums, such as the Golden Gate Sea Kayak Symposium or Traditional Arctic Kayak Symposium where high-level instructors are brought in for a few days of intensive classes.
Also, as classes progress so does the safety instruction. Every class should have a safety component to it.
Whether it’s a river rescue class or a surf zone class, getting instruction on how to be safe is important.
Don’t Forget the Fun,
 After writing this I realized I missed an important issue: FUN. I had sent a draft to Gregg Berman, a kayaking instructor, guide, and author of articles in kayaking magazines who summed it up well: “Your enjoyment can be greater with an increased skill level, whether you want to surf or rock garden or fish or watch birds. Learning to control your boat can make you more efficient so you have more energy while paddling. And wherever you go, instead of worrying over conditions or distance from shore (though some level of awareness is certainly prudent) or whether you’ll capsize, you can play. People always remark to me how much fun it looks like I’m having on the water, because my skills give me the confidence to goof off and have fun, regardless of where I’m paddling or what I’m doing”.

So instead of sitting on the sidelines, wishing you had the skills to paddle in all except the nicest of conditions, get out and take a class and become a better paddler.
 Bill Vonnegut