Swim away from chance for peace (8)

I believe the answer is:
serenity
'peace' is the definition.
(synonyms)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for serenity that I've seen before include "Peacefulness" , "Peace, tranquillity" , "Calmness" , "Calm composure, peace" , "Peace of mind" .)