Why is it so hard for people to pull boats out of the water?

This guy was obviously having big problems getting his pontoon boat out of the water. So, he enlisted the help of another truck.

They tied their rigs together and hit the gas. Success! But it was short-lived.

Watch as a chain of events happens that ends with the boat nearly back in the water and a lot of pissed off people.

Source: Free Beer & Hot Wings