Final answer:
When a PWC is shut off, it loses the ability to steer since steering requires thrust from the engine. Canoeing upstream is easier near the shore due to slower currents and downstream is best in the middle due to deeper and faster water. Flow decrease in a shower during a toilet flush is due to reduced water pressure.
Step-by-step explanation:
When the Personal Watercraft (PWC) is shut off, you will lose the ability to steer the PWC completely. The steering of a PWC is based on the thrust of water provided by the jet drive. When the engine is off, there is no thrust, and consequently, no way to change direction using the steering controls.
As for the question related to canoeing, when paddling a canoe upstream, it is best to stay near the shore because the current is generally slower and there is less resistance, making it easier to paddle. Conversely, when canoeing downstream, the middle of the stream is typically deeper and the current is more even and faster, which can help carry the canoe with less effort.
Flow decrease in a shower when someone flushes the toilet is because flushing the toilet requires a large amount of water quickly, which reduces water pressure and availability to other fixtures like showers. This sudden demand causes a temporary drop in pressure, and therefore, the flow decreases until the toilet has filled up and water pressure stabilizes.