One of two tourist paddle boats operating twice-daily from the shores. This is the Tahoe Queen, which is docked next to the Riva Restaurant and I think is somehow connected to a resort next door and to the east of the Riva.
The other paddle boat, a third iteration of the original, is the M.S. Dixie II, docks along the Nevada side. The first wasn't named Dixie ;-)
The lunch cruise ($46) and the dinner cruise ($81) are both 2½ hours in length. If you tour the resort with the 90-minute timeshare sales pitch, they might comp either of the cruise prices. We actually did neither, as a storm was approaching the one day we had left. There's always next time, right?