That's a good visual and explanation, Ranger. But...
What we're talking about is using an underwater texture and shallow water depth to make a nice gradual deepening of the water. When you turn off some of the advanced graphics, the water is no longer recognizable as water - it looks like the underlying texture, in the case of my example sandy rock and riverbed. Take another look at my earlier post with the clickable thumb of the five pictures. Water no longer looks like water with low detail options selected.