unruffled

free from emotional agitation or nervous tension; "the waiters were unflurried and good natured"; "with contented mind and unruffled spirit"- Anthony Trollope

(of a body of water) free from disturbance by heavy waves; "a ribbon of sand between the angry sea and the placid bay"; "the quiet waters of a lagoon"; "a lake of tranquil blue water reflecting a tranquil blue sky"; "a smooth channel crossing"; "scarcely a ripple on the still water"; "unruffled water"