> All that day, kids got to see Mr. Stillwater’s hair dryer running under water in a fish tank. I thought I knew about electricity and water, but what I possessed was Conventional Ignorance posing as Conventional Wisdom. Humbling.
Should I put the wifes running hairdryer into our fishtank to entertain our child?
"""Underwriters Laboratories modified its marking requirements for hair dryers after the CPSC brought to UL's attention reports of injuries and deaths attributed to consumer misuse of hair dryers. Under the modified requirements, hair dryers must be permanently. marked "Danqer-- Electrocution possible if used or dropped in tub. Unplug after using." A tag with warning instructions also is required by UL to be attached to the power supply cord."""
TL;DR insurance underwriters observed enough deaths that they believed it was wise to change a product's markings to avoid having to pay out as much money.
Assuming that the dryer continues to run, it is perfectly safe to keep it running indefinitely in a fish tanks (without fish, of course). You just have to unplug it before removing it.