Gonzalo on having quarreled with the Boatswain, realized that there was no way in which he would die from drwoning in the sea, therefore the "great comfort", as Gonzalo was sure he would not let his crew and himself drown, but he was sure that his death would come upon him due to his sharp tongue by hanging.
"This fellow" referred to here is the Boatswain of the ship, he had at the beginning respectfully asked Gonzalo and his collegues, to head back into inside along with the king and the prince as his naster could not be disturbed at that moment, else they might die in the tempest.
This scene has taken place on a ship, returning from King Alonso's daughter Claribel's wedding. Gonzalo is accompanied by Antonio, brother of Prospero, the rightful duke of milan, and Sebastian, the brother of Alonso, and the Boatswain, agianst whom, these three were quarreling.
