Thanks Alchemy.
I realized that I was wrong (your first point) , where if there's no movement, then there's no work.
For your second point, Yes, ultimately it comes down to friction, except for the heat (#2), which I didn't state clearly, comes from the motor coils. The same is true for #3, but would also include "water noise".
So now you've got me wondering: if "the friction in water due to its own turbulence is basically nil unless you have supersonic flow", then where does the heat come from? Friction of water to inner tube/channel surface?
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