A small screw top bottle wrapped in tape
a. the length in miles of the river from sea to source.
b. the number of river locks in the navigation.
c. the year that the Aust ferry closed.
d. the year the second crossing opened.
e. the number of crew on the water in the boat race.
f. the year the Holt bridge was completed.
g. the year the Upton bridge was completed.
The cache can be found at these coordinates
N52 x+1.y W002 x+2 . z
where x = e - b y = 3 (a-b) - ((d-c)+1) z = f/2 + e