WHO has known the ocean? Neither you nor I, with our earth-bound senses, know the foam and surge of the tide that beats over the crab hiding under the seaweed of his tide-pool home; or the lilt of the long, slow swells of mid-ocean, where shoals of wandering fish prey and are preyed upon, and the dolphin breaks the waves to breathe the upper atmosphere. Nor can we know the vicissitudes of life on the ocean floor, where the sunlight, filtering through a hundred feet of water, makes but a fleeting, bluish twilight, in which dwell sponge and mollusk and starfish and coral, where swarms of diminutive fish twinkle through the dusk like a silver rain of meteors, and eels lie in wait among the rocks. Even less is it given to man to descend those six incomprehensible miles into the recesses of the abyss, where reign utter silence and unvarying cold and eternal night.

To sense this world of waters known to the creatures of the sea we must shed our human perceptions of length and breadth and time and place, and enter vicariously into a universe of all-pervading water. For to the sea’s children nothing is so important as the fluidity of their world. It is water that they breathe; water that brings them food; water through which they see, by filtered sunshine from which first the red rays, then the greens, and finally the purples have been strained; water through which they sense vibrations equivalent to sound. And indeed it is nothing more or less than sea water, in all its varying conditions of temperature, saltiness, and pressure, that forms the invisible barriers that confine each marine type within a special zone of life — one to the shore line, another to some submarine chasm on the far slopes of the continental shelf, and yet another, perhaps, to an imperceptibly defined stratum at mid-depths of ocean.

There are comparatively few living things whose shifting pattern of life embraces both land and sea. Such are the creatures of the tide pools among the rocks and of the mud flats sloping away from dune and beach grass to the water’s edge. Between low water and the flotsam and jetsam of the high-tide mark, land and sea wage a never-ending conflict for possession.

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