Enemy in the Dark

THE WORLD by which they were now surrounded gave them an eerie feeling. They were familiar with the wide open spaces of the universe or the inhospitable surfaces of other worlds but rarely ventured into the deep regions of oceans. Although deepsea cruises in land-sea-air transporters had been part of their training they had assumed they would spend all their time in the comfort of a spaceship and never seriously contemplated a life underwater.As soon as they entered the water the observer had detected small semi-metallic objects moving in the vicinity of the ship. The way they moved indicated that they must be steered. Untcher tried to contact them with the short-range intercom but received no answer.The unidentified boats finally left as if they had been suddenly called back.  What happens next is part of the exciting plot of–  ENEMY IN THE DARK!