Larian Studios Forums Divinity - Original Sin Divinity Original Sin - Help/Tips/Tricks Lady in the Lake

So in pursue of white witch, i came to other dimension, and then there is this "lake" talking to me. I came to her but there is stone barrier prevent me from entering her chamber. there is a switch, but it is locked. anyone know how to unlock the switch?

near the 5 blue mushrooms, you need to dig up the key to the switch.

Thank you SIR!! is there a full guide for this game? seriously, whoever made this are crazy. this game is so hard, even looking for a single key i need 20-30 minutes to find.