How do navigators use ocean swells when stars or sun are hidden?

• A. Rely on land-based landmarks
• B. Follow migratory birds
• C. Read long-distance wave patterns to hold course when stars or sun are hidden
• D. Use magnetic cues

Answer: (C)

When celestial cues are unavailable, mariners turn to patterns in the sea itself. Ocean swells are long, regular waves created by distant storms, and they travel in a fairly consistent direction. A navigator watches how the crests line up and how the water is moving beneath the boat to infer the swell’s travel direction. That information provides a reliable reference to hold a chosen course even with stars and the sun hidden. This method leverages the sea’s own patterns as a guide, rather than relying on landmarks, birds, or magnetic cues.