Personally, I'd get bored and leave the tub before it even got that hot.

Though maybe you could do it for real using a Beast Games kinda format. Offer ten thousand dollars to anyone who can stay in a tub for 7 days (so they expect day 1 to be relatively easy), but start the boiling human experiment immediately.

Then, if everyone leaves before it gets to a boil, repeat the experiment but with slightly more money offered and continue increasing the offer until someone gets boiled alive to determine how much money you need to offer people to become the frog in the metaphor.

Or maybe if the money is raised too slowly it won't make a difference and people will keep getting out when they are too uncomfortable.

Probably not.

That’s pretty much how I bathe except with shower water.^*^

^*: I do not actually shower for 5 hours^