Though not so dark as the greater depths I visited later on, there was far less light than I had supposed. The floor of the lagoon, here at seven fathoms, was bathed in a sort of purplish twilight which enabled me to see as clearly, I should say, as on an average moonlight night ashore. But instead of being silvery, like moonlight, the light was purple, and tinged with changing shades of green and blue. The bottom was of dense reef-coral, which dies when sheltered from the breaking sea, but a hundred fantastic varieties of still-water coral grew on the dead madrepore, as vegetation grows on the inanimate earth, and its forms were those of vegetation. Close beneath me I saw little coral plants, fragile as violets or anemones; on a level with my head were leafless shrubs, marvelously colored and perfect in trunk and limb and twig; yonder a giant mushroom, ten feet across and growing on a tall thick stalk, towered above the undergrowth. Shoals of small fish, gay as the bird life of the tropics, drifted through the coral foliage or darted into the shelter of the mushrooms when larger fish passed overhead. The floor of the lagoon was irregular, seamed by gullies and rising in rough hillocks here and there, and my weighted basket lay at the edge of one of these ravines. By swimming slowly in a horizontal position I could move from place to place without great effort, and hoping to find at least one oyster before I was forced to rise for air, I swam along the brink, scanning the coral sharply for the pearl oysters I knew to be plentiful at this place. A great silver cavally, four feet long and with goggle-eyes as large as dollars, darted out of a gloomy cleft, halted to gaze at me for an instant, passed within a foot of my face, and disappeared in the shadows. The fish gave me a start; in the flurry I let go a good half of my breath, which rose in a string of bubbles toward the air. My lungs were cramped. I had reached the limit of endurance. I made for the line, seized it with both hands, heaved strongly and felt myself bounding upward like a cork. When my head broke water and I raised the goggles from my eyes, I saw that the native boy was bending over me with an air of concern. "Another moment," he said, "and I would have gone down after you. You were long on the bottom--I feared that you had been seized with cramps." "It is strange down there," I answered, a little apologetically, "the pressure--the dim light--I was so interested that I nearly forgot to look for shell and when I did look there was none to be seen."