This great little spot was once Long Bridges lido. There's not much evidence left of its former use, but there are a few random concrete bases that presumably used to be changing facilities and such, and the ladder for climbing in/out of the river. I have often seen a pheasant strutting about, but can't guarantee he'll be there when you visit. This little island on the river is accessible between the two bridges.
I've put difficulty 1.5, it is probably wheelchair accessible though the path down to the island can be pretty muddy. Take care of water's edge if with kids.
PUZZLE: This cache has a piece of information in needed to solve a bonus cache. NB you don't need to remove the object from the tube, it's stuck in place; the [small piece of] information needed is visible.