For a general sense of calmness:
* Turbulent: This implies a state of unrest, chaos, and agitation.
* Restless: This suggests an inability to relax or settle down.
* Unquiet: This emphasizes the lack of peace and serenity.
* Agitated: This emphasizes a state of nervous excitement or anxiety.
For a sense of stillness and quiet:
* Bustling: This implies a lively, active atmosphere.
* Noisy: This refers to a lack of quiet and a presence of loud sounds.
* Rowdy: This suggests a boisterous and disorderly environment.
* Chaotic: This implies a complete lack of order and control.
For a sense of peace and serenity:
* Troubled: This implies a state of worry, distress, or difficulty.
* Stressful: This emphasizes a state of mental or emotional strain.
* Anxious: This suggests a state of uneasiness, fear, or worry.
* Upset: This implies a state of emotional disturbance or distress.
The best antonym for "tranquil" will depend on the specific situation and the nuances you want to convey.