Yawing occurs when a vessel's bow swings erratically to port and starboard of its intended heading. This rotational movement around the ship's vertical axis is usually caused by following seas, heavy quartering swells, or poor steering. Excessive yaw makes it difficult for the helmsman or autopilot to hold a steady course and increases the risk of broaching in heavy weather.
Heard on the job
She's starting to yaw badly in these following seas, so keep a firm grip on the wheel.
Insider tip
A ship that yaws constantly will cover more distance and burn more fuel; adjusting trim or speed can sometimes dampen the motion.