Caumasee (Romansh: Lag la Cauma or Lai da Cauma) is a lake near Flims , in the Grisons , Switzerland . It is one of the lakes on the Flims Rockslide deposits. The lake is fed from underground sources. Its surface area is 10.3194 ha.

The level of the lake varies by approximately 4 to 5 meters along with the varying underground water flow during the year, hence reaches its minimum by the end of April when snow melting in the mountains increases. A maximum level is reached by mid July but may be topped in August even after previous falling due to summer rain.