These descents of mine beneath the sea seemed to partake of a real cosmic character. First of all there was the complete and utter loneliness and isolation, a feeling wholly unlike the isolation felt when removed from fellow men by mere distance …. It was a loneliness more akin to a first venture upon the moon or Venus than that from a plane in mid-ocean or a stance on Mount Everest: no whit more wonderful than these feats, but different.

Half Mile Down (1951), p. 148