Was it a spa bath ?
Anyhoo, hot bath, blood pressure goes up, brain says it wants more oxygenated blood than should go to feet, puts the body into a faint, head indeed goes lower despite it not being the best location for that to happen. glug, glug, glug, choke, choke, choke, etc.
Bloke at work lost his 21yo son in a hot spring in South America around 3 months ago basically the same way. He had had a few drinks with mates, they left, he stayed to look at the stars for a bit longer, and the authorities fished his body out the next day.
Those warnings on hot springs about not staying in too long are for a reason ...
Not a good idea to hot bath, hot springs, hot spa alone or for too long, particularly in a source of hot water that doesn't cool off relatively quickly making you wanna get out before your core heats up too much and your blood pressure stays artificially higher than normal for too long.
Particularly if your body and its systems have been previously weakend by various kinds of self-abuse over the years, whether it was substance abuse or by being a lyrca clad cyclerrorist 8 days a week or reading too much BTB.
So, if you're looking for a way of getting rid of granny or your crack-whore mum or some of the retirees who are driving you crazy at the hospise where you work, dial up the thermostat and timers on their hotwater system, spa, sauna, or hydotherapy pool.
regarDS