Harvard IV,
I found some data from a 1998 USGS survey of Tahoe...Thar's gold in
that there survey!
....Wanna take a ride????......"Flight" over Tahoe subscape,
http://tahoe.usgs.gov/movies.html
Read the page all the way thru, and then select . Long download times for "nominal" 'puters...but very nice resolution..right off of the maps!
Bathymetry Images
http://tahoe.usgs.gov/bathimages.html
They used a high-resolution multi-beam mapping system which simultaneously collects backscatter return( similar to sidescan sonar).
Meaning, an image interpretation based on the "shadow" of the hit .
Maybe if one could meet the operater..he could return with that
persons "gut-feelings" about data he observed.
There are more thorough downloads in file and zip.
Open File Report,
Outlining mission requirements, scan-bands, environmental interferences and resultant adjustments for success...
http://tahoe.usgs.gov/openfile.html
It's nice when 'Gubment works "with" us!
Addenda; Tahoe is not a volcanic lake, but it is "geologically-blocked"
due to 'crust upheavel',..and later "glacial gouged". My bad..I hadn't
read upon it in some time.