And I do mean the murky depths...
This cache will take you to Truss's island where you can park (mind the geese), then on the island, you need to locate a number of signs, some of which are little hard to read due to age. From the signs you will able to gather information which will lead you to the treasure you seek. This is a simple offset cache a reasonable distance away, please do not attempt to drive there as it is a private road which is barely more than a track with nowhere to park or turn around.
A= How long was Patrick Jones a member of Runnymede borough council?
B= How many bullet points under Truss's island?
C= Last number in the phone number to report any hazards?
D= What year did the city relinquish control over the river? (3rd number)
E= What year did the latest restoration take place? (last number)
F/G= For how many years did Truss pursue the interests of the corporation?
H= How far away is the lock away? (1st number)
Final location is
N51 ED.(F-H)(A-E-F)(B-G) W0 (G-H)(A-B).(A-D)(E)(D)