If this isn't very secret, you may well feel that it 'ought' to be. The three thumbs relates more to the exquisite siting of the church and its delightful, well-tended churchyard than to any outstanding architectural feature.
The creek is mud-filled at low tide when it has its own appeal but it's generally the high tide view that gets people enthusing.
This is one of the creeks off the so-called Carrick Roads between Falmouth and St. Mawes. St Just was one of the saints of the Celtic Church.