Or just buy fins in the resort pool shop like the inflatable turtle :-)
thankfully OP knows what to do for the next trip. Indeed, every place has stuff to buy. Before I rediscovered the joy of hotel pool, I bought a pair of swim trunks in the crown plaza rosemont IL gift shop. I probably bought a dress belt there as well. Worked out fine.
i know enough FTers who bring carryon only for long trips. It’s not my style and I know it’s mega possible to do.