Finally, lets talk about cavitation. Cavitation is just boiling water. Water can boil at any temperature. All liquids have something called vapor pressure. As the temperature goes up, so does the vapor pressure.
Water just has a lot less vapor than gasoline.
A liquid boils when it gets so hot that it's vapor pressure reaches the pressure surrounding it. In a pot of water, that is the pressure of the atmosphere pushing down on the water, about 14.7 psi. If there are any rough or sharp edges in the pot, the bubbles will tend to start forming there. In the intake portion of the jet pump, the water velocity is very high, so the pressure is very low. The pressure is so low that it comes close to the vapor pressure of the water in the pump.