I visited Lake Shasta in Oct 2008 to check out the historic low waters, which were at 29% of full, or about 130 feet below normal. It was a great chance to get a fish-eye view of the lake bed.
You can see the launch ramp here on the lower left (currently closed).
Here's the full view under the bridge.
Usually the river comes only feet below where I am standing. You can just see the running water in the distance.
High water lines on the supports.
Usually about 65-70 feet under water.
. . .which is normally the lake. You can see where people were driving all the way down to the lake bed.
Dried silt cracks open in the sun.
Here's an example of a typical rock formation low in the lake.
This may not be the safest place to go exploring, after all. This tunnel is normally hidden by about 100 feet of water. There was graffitti inside from the last time the lake was this low.
Watching a train pass overhead from the inside of the tunnel.
Note the water lines on the supports.
Just for reference, the place we are standing is normally the middle of the lake. We were able to drive out there on roads that have been under water for years.
Looking more like a launch ramp right now, this used to cross the Sacramento River.
Normally, this would be about 10 feet from the water line.
You can just make out the opening of one of the old railway tunnels at the end of this bridge