serene vs tranquil

serene and tranquil both are adjectives.

Word	Noun	Adjective	Verb	Adverb
serene	No	Yes	No	No
tranquil	No	Yes	No	No

As adjectives, serene and tranquil are synonyms defined as:

Other synonyms of serene include calm, unagitated.

serene (adjective)	tranquil (adjective)
completely clear and fine	(of a body of water) free from disturbance by heavy waves
not agitated; without losing self-possession	not agitated; without losing self-possession