Ride the Croc LARC ex military vehicle/boat Cairns does a drive in the CBD, in to the industrial area then in to the Trinity Inlet as a boat. Cruise along and learn about the marine history of Cairns. Tour guide talked the whole trip, lots of interesting info (even for locals!). Of course they CAN NOT guarantee you will see a crocodile (though there are many crocs living in the area!), but enjoyable trip anyway.
Great for kids through to seniors.
Would be better if it was a little longer, bit more of a drive and info in the city.