While people are doing experiments, the way a GFCI works is by comparing the current in the hot leg to that in the neutral leg. The if the difference between the two exceeds the trip current, around 5 milliamps, it trips.
What this means is that if an ungrounded person’s body is placed between the hot and neutral legs the GFCI will NOT trip because the hot and neutral legs are balanced. Trust me on this. Back in the 70’s when they were new I tested one and found out the hard way. Yes, there were beverages involved.
I wonder what would have happened if you’d dumped some salt into the water before trying this? (would you still be around to tell the tale?).
We’ve never been in the situation with the OP, though we did get a bit concerned when our carpets got drenched due to a storm / poorly designed basement drain last year.
We do have several GFCI outlets that seem to trip at random - and they control a number of seemingly unrelated outlets like the one in the main level bathroom also covers the basement bathroom and an outlet in the furnace room. Maybe that one trips because of the freezer that uses the outlet.
Another one in the kitchen trips periodically for no apparent reason whatsoever - I’m not sure anything is even plugged into that same circuit. Bizarre.
Of course, sometimes I think the wiring in this house was done by a drunken chimpanzee. We have one phone outlet that has had to be replaced, twice, because the wires seem to corrode or short out. First symptom is that the phone sounds very crackly. When we had an electrician out a few months ago, he looked and said it looked almost like the outlet had been exposed to some kind of liquid (it had not).
Used to have stand in a foot of water to flip the switch on an old Square D fuse box hanging by the wires to change the fuses when the sump pump blew it. I was always figuring I was going to get it because I was shaking in fear so badly.
Eventually got things sorted but about 6 times in one year I almost shit my pants.
Electricity hurts me more than most. Too much exposure IMO…