  Type IIP supernovae (SNe IIP), which represent the most common class of
core-collapse (CC) SNe, show a rapid increase in continuum polarization just
after entering the tail phase. This feature can be explained by a highly
asymmetric helium core, which is exposed when the hydrogen envelope becomes
transparent. Here we report the case of a SN IIP (SN~2017gmr) that shows an
unusually early rise of the polarization, $\gtrsim 30$ days before the start of
the tail phase. This implies that SN~2017gmr is an SN IIP that has very
extended asphericity. The asymmetries are not confined to the helium core, but
reach out to a significant part of the outer hydrogen envelope, hence clearly
indicating a marked intrinsic diversity in the aspherical structure of CC
explosions. These observations provide new constraints on the explosion
mechanism, where viable models must be able to produce such extended deviations
from spherical symmetry, and account for the observed geometrical diversity.
