Gonzalo shows he is a shrewd judge of character, as he more than once expresses confidence the boatswain won't let them all drown during the violent storm that opens The Tempest. He perceives that the boatswain is a tough, defiant person who will do whatever it takes to survive. He is competent and not a person who will give into fear.
While the passengers are panicking, Gonzalo tries to point out the toughness of the sailor they are depending on, saying he is more likely the type to be hanged than to give into a storm. He also says is sure that this boatswain wouldn't let them drown even it the "ship were no stronger than a nutshell."
Gonzalo is right. The boatswain does what it takes, which includes not being afraid to rudely tell the high-ranking guests to be quiet and stay out of the way. Of course, he can't overcome Ariel's magical powers, but he fights the good fight. The scene also helps characterize Gonzalo as having more sense that his royal patrons.