Lois Lamplugh

Andrew, Bruce and Celia (who are friends but not related to each other)
are home from the holidays in their small North Devon village of Crowdown.
Bruce becomes intrigued with the idea of re-building a sand yacht that
has been abandoned in Crowdown by another family. Eventually he is
successful. Meanwhile Andrew and Celia have become fascinated by
searching for the remains of a chapel that once used to be located
amongst the massive sand dunes that are a major feature of the coast.
As the year goes by the three teenagers spend different holidays
enjoying the racing of the yacht and uncovering the ancient building.
It is the latter task which dominates the second half of the book.
Together with 6 helpers (including the Allen family who feature in
many later adventures) the three friends gradually dig their way down
until the outlines of the small chapel buried for hundreds of years
are finally revealed. They style themselves the "Nine Bright Shiners"
after the words of "Green Grow the Rushes" which they sing as a sort
of work-song as the slowly clearly the inrushing sand.
Inevitably their activities are found out by some of the local
small-time villains who suspect that a treasure may be found.
There is a robbery, a chase and a successful recovery. This
leads to the discovery of something precious which makes all
their activities worthwhile.