After an hour and a half of looking we finally found the Hackney Ponds, it's one of those places of legend that shows up online but is impossible to find with maps and the directions people give are kind of hazy like.. 'it's over the red bridge and on the right'
The River lea runs all the way through but the ponds has a shallow entry and the water runs almost perfectly clear. We didn't actually swim this time, although I will next time . I took some photos of the spot itself, but also the walk as we went to some beautiful spots in our search, it really did not feel like being in London at all. I would tell you where to find it, but you know it's a secret.