Hi Noopsy,
On our first day we strolled (without map) around Plakias and found the church, bridge and the old watermill.
The second day (after we had purchased a booklet with map) and tried to find the path down from Myrthos to Plakias via the old watermill. We explored several paths going down at the west side of Myrthos, but did not find the path. During this search we made this picture (birds eye view) of the same church and old watermill.
This path is described in the local purchased walking guide 10 walks around Plakias, but most likely no longer existing.
Regards
Beachcombers