Er-Odd-Ic

You walk over to the mural and proceed to stare at it, marveling over how realistic it looks. You can swear that you can see the waves moving, as though this is not a mere painting, but a window into another world.

The room isn't as dark as a windowless room should be, but it nonetheless impairs sight of this woundrous work of art. On the far wall, next to the door, is a switch. Perhaps it connects to a light source in this room?