Another word for tranquil
Said especially of people
calm, serene, composed, agreeable, gentle, unexcited, unexcitable, placid, amicable, peaceful, pacific, untroubled, unruffled, sober, quiet, reasonable, measured, lenient, even-tempered, smooth, gentle, poised, at ease, well-adjusted, patient, cool; see also calm 1, serene.
Said especially of weather, nature, etc.
quiet, peaceful, calm, mild, soft, temperate, moderate, low, serene, halcyon, hushed, still, whispering, murmuring, pleasing, comforting, restful, tame, sedative, soothing, even, balmy, southerly, agreeable, pastoral, paradisiacal; see also calm 2, fair 3, serene. See syn. study at calm.