O Captain! My Captain!
How we cite our quotes:
For you they call, the swaying mass, their eager faces turning; (12)
The patriotic people on the shore are deeply devoted to the captain. Because they are describes as a “swaying mass” and their faces all turn at the same time, they are imagined as one patriotic body and not as a bunch of individuals (who just happen to move the same way all at the same time).