[inquest]

I think cinFLA's point is that you don't push against air and water the way you push against a wall. Rather, you accelerate the air water in the opposite direction from which you wish to move, resulting in a forward momentum on your part. Still seems like "pushing" to me, but that's the best I can glean from his statement.

[RightWhale]

you don't push against air and water the way you push against a wall.

Sure you do. It's a trivial point. Rockets act a little differently in that they carry stuff to push out the back. Cars act a little differently in that they push against solid ground. The specific mechanisms vary except that they all require two components of a medium.

[RightWhale]

seems like "pushing" to me

When down at the municipal pool, I get around by pushing on the water. There isn't much vacuum in front pulling me along. That's the low-speed case, extremely low speed in my case.