Kit's spirits bobbed "like whitecaps"
White-capped waves are quick-moving and on the surface of the water. When Kit's spirits rise at the thought of finally going ashore in America, she is excited.
Doll drifts "like a useless twig" in the current
Prudence, a young girl, has dropped a beloved and valuable doll overboard, and the movement of the water is carrying it out of reach like the current of a river might carry a twig. The water has no regard for the importance of the doll.
People look at Kit "as though she had sprouted a tail and fins"
Having demonstrated good swimming skills, Kit has astonished the Americans in the boat, who are staring at her as though she has done something shocking and unexpected.
Freedom compared to savagery
Kit is suggested to have "run wild like a savage", which meant that she learned how to swim and had freedom Puritan girls typically didn't get.
Kitten's fur as simile for softness
Mercy compares the soft texture of a shawl to a kitten's fur, meaning that it is silky, soft, and supple unlike the coarse woolen clothing she is used to.
Kit feels as though Nat has thrown her a line
Kit's eyes meet Nat's, and she feels an instant emotional connection with him along with a sense of relief. Throwing someone a line is a lifesaving technique people use to rescue a person who is drowning. Although Nat never literally rescues Kit from drowning (Kit is the better swimmer and proves it early in the book), Kit's sense of being rescued foreshadows Nat's willingness to risk a whipping to rescue her later when she is on trial for witchcraft.
