Can you take a vortex loop - akin to a smoke ring in air - and tie it into a knot or a link? The possibility of such knottiness in a fluid has fascinated physicists and mathematicians ever since Kelvin’s 'vortex atom' hypothesis, in which the atoms of the periodic table were hypothesized to correspond to closed vortex loops of different knot types. More recently, the knottiness of a fluid has re-emerged as a conserved quantity in many idealized situations (such as Euler fluids and ideal plasmas). I will tell of how to make a vortex knot and link in water, in the wave function of a superfluid (on a computer) and of what happens thence. In particular I will talk about how linking coiling and twisting interplay across scales.