I love taking cruises on Lake Mead on the Desert Princess with Lake Mead Cruises. Have gone many times over the years and have never had anything but a great time. The staff has always been excellent, and the views are simply amazing! Seeing the Hoover Dam and the bypass bridge from the water point of view is really cool, and you get pictures that you can't from anywhere else. I have been on both the sightseeing day cruises and the dinner cruises. They are both fun and relaxing. Have also been on both the paddle wheel boats in Tahoe (managed by the same company) and suggest them as well. I suggest that you check out downtown Boulder City either before or after the Lake Mead cruise as its very cool and nothing like Las Vegas. There is also a really cool Hoover Dam museum in the historic Boulder Dam Hotel that is definitely worth seeing, even if you have already been through the tour at the dam.