The depth of the lake Markermeer is 4-5m.
However the bottom is quite soft.
So all the wreckage will have sunken into the bottom.
surveys must have been performed up to a reasonable level of detail.
otherwise Defense would not have been able to asses the risks.
A likewise recovery with cofferdam has been performed in 2016 for a Wellington.
Costs ran then already into 1 million euro.
Wellington