calm, unagitated, serene, tranquil -- (not agitated; without losing self-possession; "spoke in a calm voice"; "remained calm throughout the uproar"; "he remained serene in the midst of turbulence"; "a serene expression on her face"; "she became more tranquil"; "tranquil life in the country")
serene -- (completely clear and fine; "serene skies and a bright blue sea")