Related Clues:

• Sudden snag
• Site of a wreck, perhaps
• Where a yacht might run aground
• Ocean obstacle
• Unexpected obstacle
• Military stint
• Link up
• Sea hazard
• Snorkeling destination, perhaps
• Give a thumbs up?
• A kind of knot
• Boating hazard
• Great Barrier, e.g.
• Site of a shipwreck, perhaps
• Knot that's easily loosened