My naval! I'm very thorough when showering - I absolutely hate feeling dirty. But I think the ol' belly button gets overlooked because of how concave it is.
I used to be better about it, but the whole chose of getting it all opened and unfolded just to get my sponge in there in all the nooks and crannies it has for whatever reason, then rolling it back up and folding it into its pouch, all to have like what three, four maybe six hours before it starts smelling again. It’s just not worth it.
Not that I just let it ruin everyone’s day, mind you. I’ve always got ice breakers or altoids and at least one, often two chip clips on me at all times.
Now, I don't want to alarm you, but it sounds like you have a rather unique situation if you must unfold your naval, and that it smells after 6 hours from washing it.