The BBC reported on this last night - saying something along the lines of there being a 72 hour recovery window (not sure if that means from being thrown into the lake or from being surfaced).
Quite a good report actually, they showed the drying and scanning. Apparently some documents were burned before being thrown into the lake also. http://www.bbc.co.uk/news/world-europe-26361455
It wasn't phrased particularly nicely, but it's got some reasoning behind it I think?