  We give a precise microlocal description of the singular profile that forms
in the long-time propagation of internal waves in an effectively
two-dimensional aquarium. We allow domains with corners, such as polygons
appearing in the experimental set ups of Maas et al. This extends the previous
work of Dyatlov--Wang--Zworski arXiv:2112.10191, which considered domains with
smooth boundary. We show that in addition to singularities that correspond to
attractors in the underlying classical dynamics, milder singularities propagate
out of the corners as well.
