_FluidDepthTexture not found

[josemendez]

I see. The red errors are not shown after restarting Unity.

But "Command Buffer caution" is still shown when playing example scenes.
Then I deleted Obi folder to reimport. But when I restart Unity after deleting Obi folder, Obi folder revived.
Obi folder seemed to be imported automatically at restarting Unity. 
And "Command Buffer caution" is still shown.

I don't know why I can't delete Obi folder...

Make sure you're not deleting it from outside Unity. If you do, the .meta file for the folder will linger around and Unity will sometimes re-create the folder. You must delete project folders from inside Unity.