Action: Start shower running.
Result: Spider starts running inside the cubicle. Largish. Black. Some white markings...
Now, I don't know that it was poisonous but I:
a) couldn't see the damn thing all that clearly and
b) couldn't have identified it accurately even if I could have seen it.
Hence: Eeek! Splat. (Did take a couple of goes though, that sucker was fast).