If you have ever bought a submersible pump or a pump unit you know that the so-called “free falling” of the pump (when no water is available for the pump anymore) means final breakdown for most of the pumps.
The reason is that the medium, i.e. the water, is necessary for cooling, rinsing and lubrication of many pump components at the same time. If no water is available the pump will become too hot, and a process of overheating will start and the insulation respectively the bearings will be damaged; the subsequent short-circuit will lead to a complete breakdown of the pump.