The talker has found a hearer but not a listener; and though he may talk his very best for his own sake, you will find that his mental movements are erratic: they have no fixed centre and no definite object. His talk is like the water of a canal whose banks have given way, which rolls aimlessly hither and thither, without fulfilling any useful function, though it is the same water which was so helpful and serviceable, when it was confined within clearly marked limits by the restraining force of its earthy boundaries.
People look like rivers very much: water is everywhere the same, but the rivers are narrow, fast, wide, pure, cold, muddy and warm. The people are the same. They have the rudiment of every human habit in them and they behave according to them. Sometimes they even do not look like themselves, but they still stay whatever they are.
As I turned away, I saw Holmes, with his back against a rock and his arms folded, gazing down at the rush of the waters. It was the last that I was ever destined to see of him in this world. - Watson.
Imagine a limitless expanse of water: above and below, before and behind, right and left, everywhere there is water. In that water is placed a jar filled with water. There is water inside the jar and water outside, but the jar is still there. The 'I' is the jar.