Phantastes: The Fairy Bath Puzzle

"I arrived at another hall, the roof of which was of a pale blue, spangled with constellations of silver stars, and supported by porphyry pillars of a paler red than ordinary. The whole of the floor of this hall, except a narrow path behind the pillars, paved with black, was hollowed into a huge basin, many feet deep, and filled with the purest, most liquid and radiant water. The bottom was paved with all kinds of refulgent stones, of every shape and hue. Led by an irresistible desire, I undressed, and plunged into the water. I rose to the surface, shook the water from my hair, and swam as in a rainbow, amid the coruscations of the gems below seen through the agitation caused by my motion. Then, with open eyes, I dived, and swam beneath the surface. And here was a new wonder. For the basin, thus beheld, appeared to extend on all sides like a sea, with here and there groups as of ocean rocks, hollowed by ceaseless billows into wondrous caves and grotesque pinnacles. Around the caves grew sea-weeds of all hues, and the corals glowed between. I thought I had been enchanted; and that when I rose to the surface, I should find myself miles from land, swimming alone upon a heaving sea; but when my eyes emerged from the waters, I saw above me the blue spangled vault, and the red pillars around." - Phantastes, by George MacDonald