Related Clues:

• Serenity found in 17-, 26-, 42- and 54-Across
• Stress-free
• Like the eye of a hurricane
• Pre-storm period
• It comes before a storm
• Simmer (down)
• Chilled out
• Meditation goal
• Sailboat stopper
• Sailor's nightmare
• Not having big waves
• Storm preceder?
• 0 on the Beaufort scale
• Devoid of wind
• Hard to rattle