The photograph Erick has uploaded below might have been snapped in any number of neighborhoods around the area these past few days, given the deluge wrought by Tropical Storm Isaac. It's worth noting, however, how the camera here manages to capture the human depth of focus of which Ruskin writes in the "Truth of Water" section: that is, it captures the surface of the water by a short focus on what's on the surface – the water lilies, the ripples, the reflection of the banyan (?) tree; these are in clear focus. What's blurry is what's further off – the trees in the background, their reflections in the water.
Presumably, a painter might reproduce the effect of of looking into the water, past the water lilies on the surface & the reflections of what's on the banks, by painting them blurred. But then does one paint the reflections of distant objects (eg, the trees in the very background) in sharp focus? I'm assuming that Ruskin castigates the conventional landscape painter for his handling of reflections; but precisely how are they mishandled?
Always worth keeping in mind the conventionality of our seeing. As JR points out in the passage on the sky, our notion of what the sky looks like – at least, if we are mid-19th-century viewers likely to be interested in art – is probably conditioned as much by paintings of the sky as it is by actual looking at the sky. We have some of the most spectacular skies in the world here in South Florida (compensation by the divinity, Ruskin would not doubt joke, for the absolute lack on other topographical interest). But we, as 21st-century spectators, no doubt have our heads filled as much with photographical ideas of skyness as 1st-hand impressions.