We entered the mine, which had water about ankle deep, and went about 150' in before it walled out.  This was good news, as our research proved to be accurate.

Without any real shore access near this entrance to the mine, we had no way of doing a quick scout underwater. 

We'd have to enter several hundred feet from the upper, dry mine.  We had our scooters with us, so this wouldn't be an issue.  We'd simply enter the water and scooter towards where we thought the submerged part of the mine would be located.

Visibility in the lake was ~15'.  Enough to make it possible for a 3 person to perform a search while scootering.

We searched the lake high and low for a lower mine entrance. Its not very deep so we felt like we covered it pretty thoroughly.  So we headed back to the lakeside discharge point of the local irrigation overflow. There we played with the trout on the scooters in the insane ripping flow for a few minutes before calling it a day.  I'm pretty sure those trout had never seen anything like us before and probably won't ever again.

After ~70 minutes, and exhausting the scooter batteries, we concluded our search.

No luck on this one, but the planning, preparation and search is half the fun of exploration

Through some research, we had a lead that an old mine, or portions of it, were now submerged in Conconully Lake, in eastern Washington.  

Naturally, we decided to spend a day looking for it.

We thought we had a pretty good idea of its general location, through quite a bit of time spent on Google Earth.  Using Google Earth, we had found what we believed to be part of the mine that lay above the lake.  

We made the long, 5 hour drive, arriving in Conconully around noon.  We immediately recognized landmarks we had found in our research, and found the upper portion fairly quickly.  

We pulled into the nearest turnout, grabbed some lights, spools, gps and put on our hiking boots to go look for the upper portion we thought we had identified.  We found it almost immediately.