String theory in the bathtub

<!--HTML-->I will describe a recently developed effective field theory for vortex lines and their interaction with sound, for superfluids as well as ordinary fluids. The presence of the surrounding medium makes their dynamics dramatically different from those of ordinary string-like objects propagating in empty space, leading to quite peculiar phenomena, observed in experiments and simulations. I will argue that the effective theory provides an optimal theoretical framework to understand such phenomena, and to make precise quantitative predictions about them.