foam flows versus air flows

The front edge on the wing of an airplane is specially shaped, so that when it cuts through the air fast, the wing is pushed up. The leading edge splits the air so there is an airflow over the top and bottom, but the flow over the top is faster because the curved topside is a greater distance. Because the top flow is faster there is less air pressure and you get lift.
It works under water also. The same shape keeps a surf board from sinking, when you move fast enough.
Upside down wings are put on racing cars to help keep them down on the road.
But the same wing shape works exactly the other way round when it moves through foam.

 in the figure below, the arrows indicate the direction of forces: "lift" (in this case rather "push, since it points downwards) and drag.