Placid
WordNet
adjective
(1) (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"
(2) Living without undue worry; taking life easy
"An easygoing man rarely stirred to anger"
"An air of placid sufficiency"
(3) Not easily irritated
"An equable temper"
"Not everyone shared his placid temperament"
"Remained placid despite the repeated delays"