Once you've found the cache (hard, but the hint will give it away!) look across the canl and you'll see a small outlet - this is the 'feeder' that keeps the canal levels constant, and is small tributary that comes from from Brent and the River Brent, which if you can get to - you can put wellington boots on and walk up!
N aba-fgnaqneq pnpur pbagnvare, nobhg 8 srrg uvtu hc va bar bs gur gerrf.