Does anyone know for sure its origin? Natural or otherwise.

been through there a few times and never heard of it....what is it?

bluebonnet cafe is good

Hole I had never heard of either. Maybe 1/3 to 1/2 mile below the dam of Marble Falls. It would be on the extreme upper reach of Lake Travis. It can be found mentioned on kayak forums, flyfishing forums, diving forums and has been on this forum in years past. It is an incredible depth of 100 and more ft. !!...Great fishing hole I am told. Some say it was a pit for rock or gravel quarrying. Some say it is a natural wash out due to it being just below a long geologic feature crossing the river, but I am really interest in finding out why it is there for sure. The codgers that built the dams would know, but they are gone. Maybe some sons of codgers and grandsons know....Ate at Bluebonnet cafe last Sat. with pie.It was great.

maybe similar to the west cave preserve in round mountain?...lot's of caves/caverns in the limestone around the hill country (almost drove into a big one on a guys property in Comal county one time)...that geologic theory is probably closer than the quarry...but maybe a combination thing?

Deep hole for sure. We used to slaughter the White Bass on Rattle Traps there years ago. I miss the Hill Country!