Possible Clues:

• Small iceberg
• Small iceberg; cab
• Small iceberg, one getting bigger outside loch
• Unfriendly dog maybe primarily guarding oarsman crossing lake
• Someone snarling in old horse-drawn cab
• Dog perhaps
• Hostile dog possibly a threat to fishermen
• Iceberg lettuce initially secured by nurseryman
• Good oarsman skirts tip of loose iceberg
• Mad dog