I heard that quite a few folks wondered what it is like to take one of those amphibian truck tours in San Francisco. I took the one offered by San Francisco Ducks, there's another provider called Bay Quackers.
The tour was a mixed experience. The actual ride is fun, and there are some parts that are really entertaining, like going through the Stockton tunnel with a movie theme with the grand finale at the exit. The stuff the guy said while being on the tour was OK, too. The downside is that they try too hard to be funny. You're wearing a whistle thingie and you're supposed to try to make funny duck sounds. In particular at fellow tourists outside, so you're basically doing even more recruiting than sitting in that funny piece of hardware to begin with. The water piece is fun in particular, at least the ducks let the passengers actually drive the duck in the water. I got lucky and turned out to be the last volunteer, so I got a pretty large stint. Going at odd times improves your chances to extra embarrassment with the fun stuff, and extra fun with the driving stuff.
The tour is roughly sketched on this map, and I don't think it differs a lot between the two offers. I have uploaded a few pictures, too.
The trucks are based on WWII landing vehicles, and are slow as molasses. Which is why they're called ducks, as you're sitting there like a duck waiting to get shot. The one I was in was actually a newly built one and just a year old, though.
If you took the Bay Crackers, I'd love to hear what you have to say (or on the ducks, too).