Students will explore how changing gear ratios can increase the or decrease the propulsion they get from their propeller. This activity can also be done in conjunction with the Propulsion - prop size activity in this Underwater Robotics unit.

NOTE: The RCX should never be submerged in the water.

Propellers can be bought at
http://www.hobby-lobby.com/boatprop.htm
3/16" Dive dog props work best. They can be superglued onto a LEGO axle.