My question is,
Is the lake shown in the YouTube video Clear Lake, Oregon extremely pure water by volume not counting dissolved air which might be about 1 in 20 by volume?
In case you didn't realize, even pure water probably can absorb a significant fraction visible light even in the region with the lowest absorbtivity. I'm guessing that lake has essentially the same absorbtion spectrum in visible light as pure water and that you pretty much cannot see more than 200 meters through water at all based on my observation of that video. I guess it's technically correct to say it's extremely pure but is not extremely clear. Since pure water itself is not completely clear, I cannot tell for sure by observation that it doesn't have a solute with colour in it.
I believe the lake shown in the YouTube video Adventure Oregon - Lost Lake draining into a giant hole is the exact same lake. I don't know that so I will specify that I'm asking about the one in the YouTube video Clear Lake, Oregon even if it's a different lake. According to the YouTube video Adventure Oregon - Lost Lake draining into a giant hole, the lost lake of Oregon is a seasonal lake. If they are the exact same lake, could the purity be caused by the drain hole? If the drain hole really is in the lowest part of the lake, could the fact that water is constantly draining and getting replaced by rain water prevent and dirt from getting stirred up and lingering in the water? In the video with the full lake, there was also grass on the floor of the lake which is a sign that the lake might be a seasonal like and therefore might be the same lake as the one in the other video. Maybe also because of the drain hole, any slight bit of the type of moss suited for water dies off after the lake drains and its floor dries so there's no moss to break off microscopic fragments into the water and make it appear green.