Tardigrades, or “water bears,” have been a point of scientific fascination for generations. They’ve experienced a spotlight moment in the last few years, featured on shows like Star Trek Discovery and South Park for their indomitable spirit and apparent immortality. Thanks to their myriad evolutionary adaptations, the little darlings have developed the ability to survive environmental extremes, kicking it old school in hot springs, extreme depths, the Antarctic, and even the vacuum of space. Nothing could kill these naturally occurring juggernauts.

Or so we thought.

A study published by Scientific Reports now claims that tardigrades, while survivalist little-engines-that-could in most situations, have a real glass jaw when it comes to taking a warm shower. Yes, the Achilles heel of the hardiest animal on the planet was in front of us the whole time. Per the report, water bears show a remarkably high mortality rate when exposed to temperatures between 99 and 181 degrees Fahrenheit. The standing theory is that these temperatures, especially when sprung on tardigrades which haven’t had time to acclimate, will destabilize proteins within the creature that would normally provide them with protection from the elements. Basically, after surviving five mass extinctions, tardigrades have met their match: a nice schvitz.