This dam seems to have some kind of concrete structure under the water. Perhaps reinforcement?

I have looked all over the lake and it appears everywhere in the lake. I believe it is only an artiact and is certainly not real.

This is Lake Aldwell behind the Elwha Dam; it was built years ago and dams along the whole river blocked salmon migration back to their spawning homes. Now they are starting to dismantle these dams and try to return the river to its original condition. Nice thought, isn't it? Read about it here.

So in a few years, come back when the river is gone, you will see that there are no blocks in the old lake bed!!

Thanks for your reply Hale! And thank you for the interesting link!

This is an image artifact which has been added to the list of "Underwater Images" in THIS POSTING