Classicly

Paul was not as a general thing given to bothering about hidden meanings. His diving below the surface had been chiefly as a swimmer, from early boyhood until more recent experience. He possessed a keener appreciation of surface values and the exhilaration from a good bath rather than what he might bring up by deep diving. But being young, energetic, and sincere, his very energy itself was bound to bring him down to the verge of deeper experience. In fact as the Doctor looked at him he appeared like unto one standing upon the rockbound coast of the ocean of life ready to take the plunge, whenever—he felt like it.