A Whip is the answer
Like a snake of twisted birth, Coiled ut not to strike. Hurled at men caught in the brine, Or linked up to a spike. Stops the horse that seeks to roam, Or holds a sheet out on the foam. What is it?
For now I must stay under the man who made me, but when he dies I'll be as powerful as he. They will watch and listen to what I say, then some of their money to me they'll pay.
Who am I?