617 Dam Busters question

When 617 Sqn were practising low flying over the Fens area, and at Derwent Waters, did they ever drop any of the dummy bombs between the two towers at the dam at Derwent waters, or did they just use the river and twin towers to get the two floodlight to focus at 60?. feet.
If dummies were dropped, were they ever recovered?.
I have seen the footage, as most of us have of the bouncing bomb being dropped just out to sea, and heading landwards, and as I am given to understand, they were recovered, but cannot find any info re Derwent Waters.

Lincoln. 7