Dolphin Island by Arthur C. Clarke

creature like a small sea anemone—and each
     cell had been built of lime secreted by the animal during its lifetime. When it died,
     the empty cell would remain, and the next generation would build upon it. And so the
     reef would grow, year by year, century by century. Everything that Johnny saw—the
     miles upon miles of flat tableland, glistening beneath the sun—was the work of creatures
     smaller than his fingernail.
    And this was only one patch of coral in the whole immensity of the Great Barrier Reef,
     which stretched for more than a thousand miles along the Australian coast. Now Johnny
     understood a remark that he had heard Professor Kazan make—that the Reef was the mightiest
     single work of living creatures on the face of the Earth.
    It did not take Johnny long to discover that he was walking on other creatures besides
     corals. Suddenly, without the slightest warning, a jet of water shot into the air,
     only a few feet in front of him.
    “Whatever did that?” he gasped.
    Mick laughed at his amazement.
    “Clam,” he answered briefly. “It heard you coming.”
    Johnny caught the next one in time to watch it in action. The clam was about a foot
     across, embedded vertically in the coral so that only its open lips were showing.
     The body of the creature (partly out of its shell), looked like a beautifully colored
     piece of velvet, dyed the richest of emeralds and blues. When Mick stamped on the
     rock beside it, the clam instantly snapped shut in alarm—and the water it shot upward
     just missed Johnny’s face.
    “This is only a little feller,” said Mick contemptuously. “You have to go deep to
     find the big ones—they grow up to four, five feet across. My grandfather says that
     when he was working on a pearling lugger out of Cooktown, he met a clam twelve feet
     across. But he’s famous for his tall stories, so I don’t believe it.”
    Johnny didn’t believe in the five-foot clams either; but, as he found later, this
     time Mick was speaking the exact truth. It wasn’t safe to dismiss
any
story about the reef and its creatures as pure imagination.
    They had walked another hundred yards, accompanied by occasional squirts from annoyed
     clams, when they came to a small rock-pool. Because there was no wind to ruffle the
     surface, Johnny could see the fish darting through the depths as clearly as if they
     had been suspended in air.
    They were all the colors of the rainbow, patterned in stripes and circles and spots
     as if some mad painter had run amok with his palette. Not even the most garish butterflies
     were more colorful and striking than the fish flitting in and out of the corals.
    And the pool held many other inhabitants. When Mick pointed them out to him, Johnny
     saw two long feelers protruding from the entrance of a little cave; they were waving
     anxiously to and fro as if making a survey of the outside world.
    “Painted Crayfish,” said Mick. “Maybe we’ll catch him on the way back. They’re very
     good eating—barbecued with lots of butter.”
    In the next five minutes, he had shown Johnny a score of different creatures. There
     were several kinds of beautifully patterned shells; five-armed starfish crawling slowly
     along the bottom in search of prey; hermit crabs hiding in the shells that they had
     made their homes; and a thing like a giant slug, which squirted out a cloud of purple
     ink when Mick prodded it.
    There was also an octopus, the first that Johnny had ever seen. It was a baby, a few
     inches across, and it was lurking shyly in the shadows, where only an expert like
     Mick could have spotted it. When he scared it out into the open, it slithered over
     the corals with a graceful flowing motion, changing its color from dull gray to a
     delicate pink as it did so. Much to his surprise, Johnny decided that it was quite
     a pretty little creature, though he expected that he would change his views if he
     met a really large specimen.
    He could have spent all day