The first method is called dynamic diving. This means that the model is always slightly buoyant and behaves much like a normal surface model. The model is driven underwater by applying full throttle and angling down on the dive planes. The advantage to this kind of model is that if you stop the motor it will raise quickly to the surface. On the other hand, the model must be operated a high speeds in order to keep it underwater.

The second method is called static diving. Model submarines that use this method are equipped with ballast tanks. The use of a ballast tank allows the operator to change the amount of buoyancy in the model. Ballast systems in model submarines use either compressed gas or pumps. Compressed gas is the most common system used in model submarines. In the case of a compressed gas system, a small supply of gas is carried onboard the model and is used to expel the water from the ballast tank. In the case of a pump system, a pump is used to move water in or out of the ballast tank. Both systems have limitations. Pump systems need a source of air to draw into the tank when the water is pumped out. This means that the boat must be driven to the surface so air can be drawn into the ballast tank. If the model is submerged and cannot get to the surface then you’re going for a swim. In a compressed gas system, the boat does not need to be driven to the surface for air, because it carries it’s own supply. The draw back is that when you run out of this onboard air, the model might not be able to be driven to the surface.