Can one pair replace flip-flops, shower shoes, and pool sandals?

If you want a do-it-all sandal, the Reef Water Vista is the model r/HerOneBag threads repeatedly land on — it's water-friendly, has a heel strap, and is comfortable enough for all-day walking. If you mainly need a packable hygiene layer for hostel showers, a $10 perforated EVA slide is the more honest answer.