My Master Hometime got wet regularly (5atm) and I didn't worry because JLC indicated in the manual that it was fine to swim with the watch. I had no problems. I also got my RGM (no screw down crown, rated to 5atm?) regularly wet giving my son a bath. There was soap involved as well, and I do the same with my Stowa FO LE (no screw down crown, rated to 5atm).
I won't consider buying a watch that I must worry about immersing. Because 5atm is sufficient for swimming, I have no worries about getting such a watch wet under any conditions, and I'd happily swim with one as well (just don't have that many opportunities to swim, to be honest). And I am encouraged not to worry about it because JLC says it's fine.
At the end of the day, it doesn't matter what sort of advice is given in this thread because JLC has already answered the query by explicitly addressing it in the manual. I just wanted to point out that the advice given here is considerably more conservative than JLC themselves provides.
FWIW, a screw-down crown does not provide any WR--WR is provided by gaskets, not the screw.
Cheers,
Daniel