We present measurements conducted on the oscillating interface between superfluid He-3 A and B. The measurements, made at 150 mu K, are taken at frequencies between 100 mHz, where the boundary moves almost in thermal equilibrium with the fluid, and several kHz, where the boundary motion is highly non-linear and out of equilibrium. Driving the oscillations to higher amplitudes seems to produce different friction mechanisms dominant only after certain thresholds. As yet these phenomenon have defied any explanation, theoretical or otherwise.