A magnetically-coupled liquid mixer having a drive mount secured to and extending into a mixing vessel, a vessel-external first magnet array adjacent to the drive mount, a stub shaft extending into the vessel and having a first thrust bearing surface, a driven portion rotating on the stub shaft and having radially-mounted mixing blades a subset of which is characterized by each having an opening through which liquid flows during rotation, a second thrust bearing surface, and a second magnet array, the arrays being positioned with respect to one another such that the thrust bearing surfaces are spaced apart at least in the absence of above-threshold fluid dynamic thrust forces on the driven portion, the blade-opening feature introducing increased fluid shear into the liquid.