Randall Garrett, Anything You Can Do
“ To a human being, the cold expanse of water that gleamed like ink in the light of the Nipe's illuminator would have been a barricade as impenetrable as steel. But to the Nipe the tidal pool was simply another of his defenses, for it concealed the only entrance he ever used. He went in after adjusting his scuba mask and began swimming toward the opening that led to the estuary of the sea, his eight strong limbs working in unison in a way that would have been the envy of a rowing team. ”
