Regarding the reason for long classes, there is also a disagreement about what needs to be taught in a basic open water class and what can be reserved for later instruction.
For example, unless I am mistaken, DCBC has altitude diving details and diving with tides as a part of open water classes. Because I do my OW classes at a high altitude, I do show OW students how to adjust for altitude when they plan their dives. I only do this when conducting the OW dives at altitude, though; if the students are taking a referral to a tropical resort, I only teach the little bit that is in the book, because more than 90% of my students will never dive locally and will never need to adjust for altitude. For a similar reason, because we don't have a lot of tidal variation in our local lakes, I don't talk about it on the OW dives. In fact, in the nearly 1,000 dives I have done in many places throughout the world, there has only been one day when I needed to take tides into consideration when I dived, and I prepared for it when that day came. I am quite sure at least 90% of my students will never dive where tides will be an important factor. If I teach them how to deal with it when they are in OW, that 10% who
might need it years in the future will have forgotten what they were taught by then.
Similarly, Thalassamania's students leave his OW certification able to tie a bowline underwater with one hand while wearing 3-finger mittens or dry gloves. That's impressive, and it shows the amount of learning in the course. Now, in all my dives, I am not sure I have ever seen
anyone tie
any knot under water, except in a class that required them to tie a knot under water. I have certainly never been in a situation where it was necessary to tie a bowline with one hand--I even have trouble imagining what that situation would be. I also doubt that more then a couple percent of my students will ever see a 3-fingered mitten or dry glove, let alone wear one while tying a bowline with one hand. That's another skill I think can wait until later in their education.
I think that a lot of people looking at the really long courses will be able to spot some other instruction that probably can wait until later.
But it is not just that learning skills that aren't needed adds time to the curriculum. It also makes learning the stuff that really is important less efficient and less effective as well.
The educational principle of interference tells us that the process of learning things we don't need to know interferes with our ability to learn the material that is truly important. The added learning makes it harder for us to remember the rest of the material as well. We have a harder time (and thus more time on task) learning the important stuff because the unimportant stuff interferes with our learning.
