You may need to adjust
the 'Draft' (How deep it sits in the water) of the steamer so that the
paddle is in the water. This is done by adding some water to the bottles.
This exact method is used in real ships and called 'Ballasting'.
To make the Steamer go further and
slower try to regulate the speed of the paddle by attaching a plastic
flap to the bottle that the paddle pushes against each time it turns.
If you visit a lake or pond attach
a long piece of string to the steamer so you can pull it back at the end
of its journey.