Related Clues:

• Titanic's undoing
• Big chip off the old block?
• Variety of lettuce
• Cold mountain?
• Glacier offshoot
• Floating ice mass
• Floating hazard
• Glacial marine threat
• Type of lettuce
• North Atlantic hazard
• Arctic chunk
• Frozen floater
• Shelf breakaway
• Glacial floater
• It's mostly underwater