left red rear light for T89 is under water

Moinsen, so, today one of the acquaintances noticed that my left rear light, i.e. the part that you can retrofit from the B4 Avant so nicely in red, is about 4 cm high under water. Was shortly before in the washing system. He only said “drill in a few drain holes down there” which I don’t quite like yet. GIBt ́s another trick? So again is not removed, then it will certainly leak back in. Can you just drill with a 3 drill bit carefully pure Then the Plexiglas bursts or does it burst? Thank you and greeting Markus