I'd heard that below Walton bridge was the deepest but I got 27ft by Desborough sailing club - Halliford Bend is the bend by Gibbs Marine (At least thats what i've read) and there's a big hole there as well. I'm guessing that the depth of the bends on the old river at Shepperton may be because of the Desborough cut taking the majority of the silt down the river with 'clean' water scouring out the bends.