adjective

(of a person) calm and self-controlled.

outwardly they are cool, calm, and collected

calm,cool,and collected,as cool as a cucumber,cool-headed,self-possessed,composed,controlled,self-controlled,poised,serene,tranquil,relaxed,unruffled,unperturbed,unflustered,undisturbed,unagitated,unmoved,unbothered,untroubled,equable,even-tempered,imperturbable,placid,quiet,sedate,unexcitable,impassive,dispassionate,unemotional,phlegmatic,stolid,unflappable,unfazed,together,laid-back,nonplussed,equanimous