Related Clues:

• Hard to rattle
• Storm's predecessor
• With nary a wave
• Bane for sailors
• Zero on the Beaufort scale
• Cool as a cucumber
• Exhibiting equanimity
• Smooth, as seas
• Like Type B personalities
• Composed and collected
• Peaceful and still
• 'After a storm comes a ....'
• Peaceful, tranquil
• Composure or serenity
• Peaceful, not excited