Within the context of Act 1, Scene 1, we learn that the boatswain is a confident and capable sailor. When Alonso and Antonio come calling for the Master of the ship, the boatswain tells them to get back to their cabins and to stay out of the way. At first, Gonzalo is offended, telling the boatswain to remember who is on the ship (the king and his councilors). But the boatswain, thinking practically, tells Gonzalo that regal authority has no place on a boat and certainly can not control the weather itself:
You are a councilor; if you can command these elements to silence and work peace of the present, we will not hand a rope more. (I.i.18-20)
The boatswain is saying that if he (Gonzalo or the king and his men) can alter the weather simply based on their regal authority, go right ahead. If they can not, they are advised to get back to their cabins. Gonzalo gets comfort from the boatswain's logic. He also shows a superstitious side, claiming that the boatswain looks like someone born to die on the gallows; therefore, not at sea.
Sebastian shows his temper, calling the boatswain an "incharitable dog." Antonio also shows his contempt and chastises the boatswain, who is just trying to save the ship (and all of their lives). Gonzalo, being fair, replies that he trusts the boatswain will not drown, indicating his trust in the boatswain and in his superstition. Gonzalo is also the only one of the king's councilors to offer help. Antonio and Sebastian either get in the way or they criticize the ship's crew.