I have operated seagoing vessels for 33 years. They operate in as deep as water as you like, hundreds of miles from land. They also operate in as dangerous waters as you like, in narrow channels lined with granite and basalt, day and night, day after day. We sit on watch, and it has never been a problem.
I went to to an academy like yourself, where sitting on watch was verboten. The concept is as antiquated as calling left and right port and starboard. And it exists for the same reason: tradition, not reason.