The horizontal port or starboard movement of a vessel is called __________.

Correct Answer: Option B — sway

Vessel motions are defined by six degrees of freedom. Sway refers specifically to the linear, side-to-side horizontal movement of the hull along the transverse axis. This is distinct from heave (vertical), surge (longitudinal), roll (rotation about longitudinal), pitch (rotation about transverse), and yaw (rotation about vertical).