The term 'SWERVED AT SEA' can be solved by the five-letter word 'YAWED'. Yawing is a type of motion in which a vessel or aircraft turns around its vertical axis, and is often used to describe the movement of a boat on the water. When a boat yaws, it swerves from side to side, making it difficult to maintain a straight course. This type of motion is common when sailing in rough seas, and can make it difficult to stay on course.