Placid
What it means
Meaning 1
Calm and not easily agitated in manner or temperament.
Reach for it when describing steady quietness without implying passivity or lack of feeling
The placid horse waited while each child learned how to hold the reins.
Meaning 2
Smooth and almost undisturbed in appearance.
Reach for it when describing still water or a similarly tranquil scene
The placid inlet reflected every mast before the wind rose.