  We consider complex 3D polarizations in the interference of several vector
wave fields with different commensurable frequencies and polarizations. We show
that the resulting polarizations can form knots, and interfering three waves is
sufficient to generate a variety of Lissajous, torus, and other knot types. We
describe the spin angular momentum, generalized Stokes parameters and degree of
polarization for such knotted polarizations, which can be regarded as
partially-polarized. Our results are generic for any vector wave fields,
including, e.g., optical and acoustic waves. As a directly-observable example,
we consider knotted trajectories of water particles in the interference of
surface water (gravity) waves with three different frequencies.
