I see what you mean. The boxes can have different states: floating. Floating= -1 means the box is on the floor with water from below. 0 is a box that is pushed in the water. They changed the state, depends what happend. Other states has to be added for other possibilities, like pushing a box out of the water. The box floats because the gravity is 0.
I will make comments in the capx what the events do. So you can alter it like you want.