Related Clues:

• It's just below the waves
• Keel scraper
• Canoeing challenge
• Underwater sandbank
• Wreck site
• River vortex
• Type of knot
• Coral habitat
• Snorkler's interest
• Snorkeling spot
• Mariner's peril
• Diver's place
• Site of a wreck, perhaps
• Where a yacht might run aground
• Mini-maelstrom