Not quite a WC but you will need to pour water into the right hand hole and be ready to catch the small dowel on the other side!
Of course this is a Quirky Cache so it's not quite that simple!!!!
There are a series of holes in the pipe underneath that will allow the water to pour out unless the finder stops it.
With three fingers placed over the holes in the underside they can try again, the dowel will provide the required digits for the combination lock whilst the holes will allow the water to drain.
A suitable waterproof box, log book and pencil will be provided, woodscrews and a spare dowel are also included.
Youtube Clip - https://youtu.be/QBGyvs_VbWI