Here was today's question; ". . for a subscriber/boating newbie here; I noticed in your lake travels, there are these red and green buoys, to which you always pass between them .. why is this and what is their purpose?"
The long and short of the Red & Green markers is to indicate where safe water is. As one cannot 'see' how deep a given area of a lake, river or canal might be, the buoys (floating) or day beacons (land based) indicate the edge of a safe way for navigation. Used in conjunction with marine charts (paper or digital), mariners can safely pass through an area where the water is shallower than what is otherwise encountered in a given area.
That said, different boats need different depths to pass through a waterway without risking running aground and that's where the charts come in. The captain of even the smallest boat must be aware of how much draft their vessel draws - how deep in the water it sits - as well as other factors that might determine what a safe depth might be fro navigating.
For example, our current boat 'Boogaboo IV' draws approximately 40" of water, with an average load. Load refers to all the weight on the boat, including the boat itself, plus other considerations such as fuel, water, passengers, gear, food and yes, even beer ;-) As well, that draft (the depth of the boat in the water, not the beer on tap) will be greatly affected by sea conditions. If we were traveling though rough water, our boat could begin to pitch up and down, making the average depth of water we were traveling through vary considerably, depending if we were on the crest or bottom of each wave. So, if we were traveling through water with only 4 feet of depth and it was wavy, we could bounce up and down enough to touch bottom. And that's not a good thing! Also, if a passing boat were to throw off a large wake (it happens all the time), we could (and do) get bounced around.
For all of the above reasons, it is imperative one knows where they are and can relate to their proximity to danger, as well as changing sea conditions. And that's where those red and green markers come in.
So, why red and green, you ask? I'll tell you. In North America, as well as other parts of the world, we follow the Red-Right-Return system of telling us which is the safe side of a given marker. In MOST cases, heading upstream (against the current), the red marker is kept to the starboard, or right, side of the boat. When heading in the opposite direction, the opposite is true and one would then keep the green markers on their starboard side.
Confused? Don't worry, it gets better. When going through areas such as Georgian Bay, that all goes out the window. Throw in other 'Aids To Navigation' such as yellow Cardinal Buoys, black (or red) and white Fairway Markers, Red/Green/Red OR Green/Red/Green Bifurcation Markers and (sometimes) land based Range Markers and you will soon realize that there's lots to learn about boating for the serious cruiser!
Unfortunately, many boaters are blissfully unaware of what many of these things mean - or the meaning behind them
I should really start a video series on how to learn these things and how they are put in to practice to help folks out. There is also something called 'The Rules Of The Road', which plainly lays out who has the right-of-way when on the water. Sadly and frustratingly, there are many, many boaters who don't have a clue what that means, or how to employ the rules to maintain safety. Here is a quick video I posted last summer after I got ticked off by someone who was in the aforementioned column of not knowing;
I hope my long winded overview on this helps you better understand what goes on. If not, at least it may inspire to you learn a bit more. . . And now you also know why I put this off until I had a bit more free time ;-)