We will present the experimental realisation of a mixture of Bose and Fermi superfluids. Our mixture is composed of a weakly-interacting 7Li BEC at equilibrium with a 6Li Fermi superfluid in the BEC-BCS crossover. 
To study the properties of this mixture we excite oscillations of the center-of-mass (dipole modes). In a regime of small relative velocity we observe long lived oscillations of the two superfluids. By performing a spectroscopy of these modes we measure the coupling between the two superfluids. When the relative velocity between the two superfluids exceeds a threshold, we observe a strong damping of these modes, compatible with a critical velocity for the relative motion of the two superfluids.