The snowbirds have flown the coop, the summer swelter has peaked, and we can picture no better staycation oasis than lapping in luxury at a hotel swimming pool. Hear us out: We don’t mean renting a room before you soak (although you can). We mean buying a day pass — a flat-fee passport that grants all-day access to swanky hotel pools, spas, hot tubs, beach access, chairs, fitness rooms, even free cocktails and water in some cases — without splurging on an expensive overnight stay.