As has been established in another question, although the four champions had to face really difficult challenges, the strong implication is that nobody in the audience could directly view their actions.
The first task makes the most sense to me. It seems to be quite entertaining for the audience. They could see the fights of the champions with their dragons but the second task had the audience watching the Black Lake for one full hour. Since Dumbledore had to question one of the merpeople about what happened, I don't believe that anybody was able to witness anything except when each of the champions reappeared on the surface.
The same goes for the third task. The audience watched the walls of the maze for the most time. Mrs Weasley and Bill came to the castle specially to watch the third task, but I don't think that there was anything interesting to watch at all.
So, if no-one could see anything, in what way was the Triwizard Tournament meant to be entertaining for the audience?