Millions of readers have enjoyed the books of Piers Anthony, including (but certainly not limited to) his undeniably popular Xanth and Blue Adept series. Now, in collaboration with celebrated nonfiction author Clifford A. Pickover, he brings us a disturbing tale of our own world, and the strange creatures with whom we share it.    It is said, and truly, that there are more things under heaven and earth than there are almost anywhere else; true as well that many of them lurk, unsuspected, far below the surface of the planet's ocean. For thousands of years, mankind has simultaneously trusted in the sea's proverbial generosity and used it as a dumping ground, trusting that in its vastness his garbage will be swallowed up and forgotten. But that was never really true. And now, in an age when the overcrowded Earth swarms with hungry inhabitants whose waste chokes even the sea, whose greedy demands overtax its seemingly endless bounty, strange things are born in the ocean's deeps-strange things that the ocean throws back upon the land..