What are the possible reasons for a bunch of dead tree trunks in a lake 20-30 feet from shore?

Question

The area is in draught so it's unlikely, put possible I guess, that the lake expanded onto land the trees were one. The trees themselves are quite tall - up to perhaps 50 feet high, but all the bark is missine and there are only naked branches above.

Answer 1

You have, in fact, provided the most likely explanation. That is, the lake level rose at some point in the past, either due to human activities or due to natural ones (e.g,. beaver dam downstream) -- there really is no other explanation for why there would have been have a number of healthy trees (i.e., healthy enough for long enough to attain statures of 50 ft.) living in an area. Indeed, you may be looking at what may have been simply a stream or river basin in the past. Given their size, that area would have supported those trees for quite some time, prior to the ground becoming first waterlogged and then submerged.

Answer 2

the trees are probably there to create a habitat for fish.If you have any idea how to fish you would realize that they gather around things in the water. thats why fishermen  fish in weeds,fallen trees,dock ramps,anything that will give fish the upper hand. then comes the mighty fishermen,with baited hook,he casts into those weeds and his hook gets tangled into that f******* tree branch and the big one gets away.