Couldn't agree more. We own a 23' power boat now that we keep in Beaufort,NC. We took an online (BoatUS) safety course before we bought it. We hope to take a trawler specific training course next spring. This one will be more about acquainting ourselves with trawlers if we are still interested we will take more detailed courses as we get closer to retirement in late 2019.
I took the online courses and they were helpful, and I also had to train with an instructor for around 20 to 25 hours before my insurance company was comfortable letting me operate the boat without an instructor.
BUT, there is no substitute for just getting out there and doing it. Just make sure you have the proper safety equipment (and know how to use it), and take a baby step approach to sea conditions.
The swells we experienced a week ago would have given my wife and I a bit of anxiety 9 or 10 months ago when we first got the boat, and now they are no big deal.
That said, there are sea conditions that many on this forum would not be worried about that would probably terrify me. In fact I'm sure that's the case.
My goal is to experience things in baby steps and work up my confidence in myself and the boat gradually.
Of course, sea conditions can always be a bit of a surprise, so I watch the forecast very carefully and assume that the conditions will be worse than forecasted, leaving a margin for error. I also take into consideration that at this time the boat can likely take more than we can, so if we were to find ourselves in 10 foot seas instead of 5, we'd likely be fine. Especially since we have a liferaft and EPIRB.
But if I see a forecast of 5 to 8 foot seas at 9 seconds, I'm assuming I could easily run into 12 footers at 6 seconds and I'm staying home. 4 to 6 at 9 seconds, I would probably head out and feel things out.
Point is, I typically build a margin of safety for the unexpected, especially given my lack of experience.
As boaters gain more experience, they tend to operate at a narrower margin of safety (relative to a novice), or get lazy. My assumption, although I could be wrong, is that most accidents happen to very inexperienced, and very experienced boaters.