This question can be answered through refering to the character of Bernard, who, compared to his other fellow citizens, is decidedly odd. One of the reasons for this is that he, unlike everybody else, seems to really dislike being with other people and actively seeks out opportunities to be by himself and alone. Note how he responds to Lenina's efforts to force him to socialise:
"In a crowd," he grumbled. "As usual." He remained obstinately gloomy the whole afternoon; wouldn't talk to Lenina's friends... and in spite of his misery absolutely refused to take the half-gramme rasberry sundae which she pressed upon him.
What is most interesting, however, is that when, as Bernard and Lenina return from this date, Bernard hovers over the waves, both characters have very different reactions. To Lenina, she describes the sight of nature as "horrible," and we are told that she is "appalled by the rushing emptiness of the night." To Bernard, looking at the sea makes him feel "as though I were more me... More on my own,not so completely a aprt of something else. Not just a cell in teh social body." To Bernard therefore isolation is something that he actively seeks because it helps him stress his individuality, which is of course in complete contrast to the values of his day and time, as Lenina's reaction to this suggests.