Blue pond

As in a pond that sleeps o'erhung by trees,
Two things at once in many a soul one sees: --
The sky, which points, the surface pure and calm,
With all its rays and clouds the heart to charm;
And then the depth, slime, hideous, dark, and dead,
Where foul black reptiles swarm, and vaguely tread.

Victor Hugo, "As in a pond".