serene
adjective
calm, peaceful, or tranquil; unruffled.
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
I decided suddenly that the captain and crew must be a set of nincompoops, who had lost their heads, and, not knowing what to do, were unserenely doing nothing.
From The Ghost A Modern Fantasy by Arnold Bennett