Final answer:
When the throttle is set to idle or the engine is turned off in a PWC, the vehicle will slow down and eventually stop due to water resistance and friction.
Step-by-step explanation:
When you put the throttle to idle, or shut off the engine on a forward-moving Personal Watercraft (PWC), the engine stops providing thrust, and the PWC will gradually slow down due to friction and water resistance. The engine of a PWC, likewise an electric motor, behaves in a way where it draws more current initially and then balances itself as a load is applied or reduced. However, the comparison between a PWC's engine and an electric motor's behavior isn't direct, as a PWC typically uses an internal combustion engine and its response to a lack of throttle or being turned off would involve the reduction of power output, leading to deceleration. Furthermore, if an engine is idling, it still operates and uses minimal fuel to maintain its operating state, providing a little bit of power, hence the PWC might still move forward very slowly or simply stay in place if other forces are at play.
An idling engine maintains minimal power, whereas a shutdown engine cuts off power completely. This behavior is part of the engine's operation similar to how electric motors manage load and current.