Related Clues:

• River hazard
• Navigation hazard
• Keel scraper
• Underwater sandbank
• Hazard to navigation
• Boating hazard
• Spit, e.g.
• Maritime hazard
• Shipwreck site
• Helmsman's challenge
• Shallow sea area
• Marine hazard
• Underwater hazard
• Navigational hazard
• Tideland