I am not a microbiologist. However I do know that bacteria are pretty resilient, and most pathogens and parasites can live for at least a few hours outside of a host. Plus your skin is really not all that smooth at a microscopic level, there are all sorts of little nooks and crannies to hold onto.
Drowning wouldn’t really be a concern for them, imo, but additives like chlorine are specifically meant to be disinfectants.
Dating sucks. For every nice person you meet and make a connection of some sort with there’s three or four who drop off the face of the planet. I get it’s easier to just ghost but it’s pretty shitty. (And this is speaking as someone with social anxiety who has definitely ghosted before lol oops)