placid

(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”

not easily irritated

• “an equable temper”
• “not everyone shared his placid temperament”
• “remained placid despite the repeated delays”

without untoward incident or disruption

• “a placid existence”
• “quiet times”

taking life easy

• “an easygoing man rarely stirred to anger”
• “an air of placid sufficiency”