Though elephants have stood for their full-lengths, the living Leviathan has never yet fairly floated himself for his portrait. The living whale, in his full majesty and significance, is only to be seen at sea in unfathomable waters; and afloat the vast bulk of him is out of sight, like a launched line-of-battle ship; and out of that element it is a thing eternally impossible for mortal man to hoist him bodily into the air, so as to preserve all his mighty swells and undulations.
But he breaches!
Melville was an early adherent of the "Jaws" principle: keep the monster mysterious and unseen until the end.