tranquil

adjective2

1. •
   Free from emotional or mental disturbance.

   • Some time passed before I felt tranquil even here: I had a vague dread that wild cattle might be near, or that some sportsman or poacher might discover me. — 1847
2. •
   Calm; without motion or sound.

   • […]that the streams which did form were clear and tranquil because fed by perennial springs from the underground supply; and that in their tranquil waters extensive peat bogs formed. — 1921