It looked harmless enough. Yet when a man was subjected to this condition for any length of time, he became susceptible to the strangest sensations. The experiences of past test subjects were amply documented in textbooks on experimental psychology; yet while nothing prevented one from reading up on them, the experiences themselves were too varied to be of much help. One-third of the candidates were lucky to last three hours; five or six hours was considered exceptional. Perseverance had its rewards, too, as the summer training assignments were awarded on the basis of the class grade list: the one with the highest grade was assigned a “special” mission, rather than a routine assignment at one of the many circum-Terra stations. But there was no way of predicting who would “tough it out” and who wouldn’t; the “dip” was designed to test severely the subject’s psychological stability.

Pirx got off to an auspicious start, disregarding the fact that he unnecessarily kept his head underwater before the mask was installed. In the process he consumed a quarter of a liter of water that, as he now had occasion to verify, was treated with ordinary salt.

Once the mask was in place, his first sensation was of a slight buzzing in the ears and of being immersed in total darkness—his eyes were kept forcibly shut by the mask’s tight fit. He relaxed his muscles and was gently buoyed by the water. Then something unexpected: an itching sensation in his nose and right eye. Now what? He couldn’t very well scratch through the mask. Hm. Nobody ever reported having an itch before. Maybe this was to be his own special contribution to experimental psychology. He rested, perfectly poised, the water neither warming nor cooling his naked body. Before long it was completely lacking in any sensations. One wiggle of his toes would have told him they were wet, but he also knew that hidden in the ceiling was a video recorder and that every twitch of his body meant a minus point.