Channel.

I hated to take my eyes off the sea, even for a moment. If you have
ever been driven at sixty miles an hour over a bad road, and felt that
if you looked away the car would go into the ditch, and if you will
multiply that by the exact number of German submarines and then add
the British Army, you will know how I felt.

Afterward I grew accustomed to the Channel crossing. I made it four
times. It was necessary for me to cross twice after the eighteenth of
February, when the blockade began. On board the fated Arabic, later
sunk by a German submarine, I ran the blockade again to return to
America. It was never an enjoyable thing to brave submarine attack,
but one develops a sort of philosophy. It is the same with being under
fire. The first shell makes you jump. The second you speak of,
commenting with elaborate carelessness on where it fell. This is a
gain over shell number one, when you cannot speak to save your life.
The third shell you ignore, and the fourth you forget about--if you
can.

Seeing me alone the captain asked me to the canvas shelter of the
bridge. I proceeded to voice my protest at our change of destination.
He apologised, but we continued to Boulogne.

"What does a periscope look like?" I asked. "I mean, of course, from
this boat?"

"Depends on how much of it is showing. Sometimes it's only about the
size of one of those gulls. It's hard to tell the difference."