system
Given the following post, respond as if you're commenting on Reddit:
human
Would paddling a canoe work if water had no viscosity?

Viscosity is the frictional force internal to a fluid.

What would happen if one was paddling a canoe in a fluid with 0 viscosity? Would it just be the equivalent of throwing water molecules through a vacuum?
gpt
There are forces at work here other than fluid to fluid drag (viscosity). As you're swinging the paddle through the water, each water molecule in its path needs to somehow get on the other side of the paddle. Since the water has mass, and thus inertia, moving around the paddle requires some force. Specifically, getting out of the way of the way of the paddle requires positive pressure (to push the water out of the way), and filling the void behind the moving paddle requires negative pressure. 

None of these processes require viscosity to operate. It's similar to the heating of the air in front of a space capsule entering the atmosphere, where the heating is not due to friction in the air as much as the air's inability to get out of the way fast enough.