The captain gives Viola information about her brother, and whether or not he drowned.
Viola gives the captain money because she wanted to expressed a sense of gratitude for giving her hope for the future and provide many wonderful blessings to boost her optimism. The captain wanted Viola not to give up hope and give her a fresh sense of fulfillment by telling her that her brother was safe and sound and he said that:
True, madam. And, to comfort you with chance, Assure yourself, after our ship did split, When you and those poor number saved with you Hung on our driving boat, I saw your brother, Most provident in peril, bind himself, Courage and hope both teaching him the practice, To a strong mast that lived upon the sea, Where, like Arion on the dolphin’s back, I saw him hold acquaintance with the waves So long as I could see.This gave her a mental image of her only brother surviving this huge disaster and it really enriches her life, proving it to be a blessing in disguise