What prompted men to run here and there?

From the text:

As we got nearer to the turn of the land the reefs began to be sown here and there on our very path; and Mr. Riach sometimes cried down to us to change the course. Sometimes, indeed, none too soon; for one reef was so close on the brig’s weather board that when a sea burst upon it the lighter sprays fell upon her deck and wetted us like rain.