It is necessary that the audience believes that the iceberg is only the bit above water.
In fact you WANT them to believe that the performance is only what they can see.
Then you find out that they do believe it.
What happens when working with an audience is that you create an illusion and the audience believes in the illusion.
The downside is that you made them believe that what you did was simple.
Most people prefer to believe that the performer is what they call ‘talented’ rather than that the performer did a lot of work.
They then hugely underestimate what they are asking of you when they say: “Could you just do that all over again please?”.