The moment where legs are bend for the jump, as the count goes on...and gets closer to the final "Bungee shout", the body starts to prepare itself with a bust of adrenaline, its a natural impulse.

You are now fliying down, hundreds of miles per hour, a couple of seconds...feeling the gravity, connecting with the forces or nature.

After the first bounce, the expression of the face will change from deep excitement to an honest natural smile... once the self and the body realizes how safe this is... after that, you won't be able to stop wanting more bungee...