Related Clues:

• See 18
• See 12
• Calm sea
• Calm - ocean
• Serene - ocean
• Calm (waters?)
• Conciliatory — calm
• Seeking peace between China and the US
• Peaceful ocean
• Peaceable
• World's largest ocean
• Hawaii's ocean
• The "P" in "CPR"
• Main steam locomotive?
• Non-combatant in the main