Becalm

17 clues
Quiet
Chill
Soothe
Steady
Make quiet
Chill out!
Don't panic
Tranquilize
Make relaxed
Crisis advice
'Do not panic!'
Keep motionless
'Stop panicking!'
Deprive of sail wind
Immobilize at sea, in a way
Exhortation for a panicky person
Leave a sailing vessel unable to move for lack of wind