Finding Nemo scene

I just saw a scene in Finding Nemo, in which Nemo, inside a polythene bag contaning watter tries to roll the bag over by hitting its walls from inside. I wonder if its really possible to do that. I thought the conservation of angular momentum (along with Newton's 3rd law) would mean that the the force created by Nemo by flapping its fins to hit the polythene wall from inside the bag would cause an oppisite linear force and angular torque preventing the bag from moving. This is certainly true if the bag is placed on a frictionless surface. The friction between the bag and te table surface ubn the practical case bring non-idealities into the system and I'm beginning to wonder if the scene is indeed consistent with Newtonian mechanics.