I watch’d the water-snakes:
They mov’d in tracks of shining white,
And when they rear’d, the elfish light
Fell off in hoary flakes.
Within the shadow of the ship
I watch’d their rich attire:
Blue, glossy green, and velvet black,
They coil’d and swam; and every track
Was a flash of golden fire.
Coleridge, The Rime of the Ancient Mariner