Related Clues:

• Snorkeling destination, perhaps
• A kind of knot
• Boating hazard
• Great Barrier, e.g.
• Site of a shipwreck, perhaps
• Lagoon creator
• It might be just below the surface
• Coral group
• Snorkeler's heaven
• Scuba diver's lure
• Great Barrier __
• Ship hazard
• Underwater habitat
• Hazard for a hull
• Atoll barrier