Been to a few swimming pools in Hsinchu and none of them allowed flip flops or shower sandals in locker rooms/shower/pool areas which i personally find rather unsanitary if not disgusting.
It’s very easy to catch athletes foot and other fungus if feet aren’t protected in wet, public conditions.
Every pool has different rules. But I think the common rule now (at least in Taipei) is to only allow flip flops in the shower area but not in the pool area.
I got athlete’s foot about three years ago (or was it longer?). I’m almost positive I got it at the swimming pool at Nangang Sports Center. Never had it before. It took me some months taking good care of my feet to get rid of it.
I have medicine for athlete’s foot and apply it whenever I feel some itching that doesn’t seem right. So far, so good, but I’m still paranoid.
I think the rule is partially to keep people from wearing their slippers in off the street.
Should be okay if you have standard shower slippers and only wear them in the shower and locker room area.