This might sound weird but this is an honest to god scientific diy test.
Go to your shower, switch the head to high pressure mode, spread your cheeks and see what happens.
The short answer is that the sphincter (asshole closing muscle) is really good at it’s job, which makes sense when you consider that even pretty loose poop can be held back for hours while gravity does it’s best to pull it out. So your sphincter is pretty strong and can handle some significant pressure, much more than your lips, so if you can keep the water from entering your mouth, your butt is fine.
This might sound weird but this is an honest to god scientific diy test.
Go to your shower, switch the head to high pressure mode, spread your cheeks and see what happens.
The short answer is that the sphincter (asshole closing muscle) is really good at it’s job, which makes sense when you consider that even pretty loose poop can be held back for hours while gravity does it’s best to pull it out. So your sphincter is pretty strong and can handle some significant pressure, much more than your lips, so if you can keep the water from entering your mouth, your butt is fine.