P.F.
We love the outdoor pool at the St. Louis Park Recreation Center. They have a large zero depth area AND a sandbox/ play area nearby, and there's a "5 and under" playtime on weekday mornings when the place is not overrun by older children. It will cost you a little $, but for itty bitty ones there's no fee. See http://www.stlouispark.org/aquatic_park.htm
Granted, it's not indoor, but for the next two weeks it's the best thing around.