We don't know why, but this ship of the Canadian Coast Guard was plowing back and forth, back and forth for about an hour one afternoon. The season was late, the weather was bad, and the seas were rough, so the bay was empty. In chugged this ship, and it started going back and forth in a roughly 400 meter line. We spent some time guessing what it was doing but came to no satisfactory conclusion.
The best theory I heard was that junior sailors were practicing their low-speed manoeuvring skills.
The Coast Guard is a great bunch of folks but they occasionally do curious things.