The pig swim is because the Bahamas got famous for the Exuma pigs.  Which were not a tourist trap, instead they were on a remote island that private boat owners would find.  They would feed the pigs and share pictures.   So now, tourists want the pig experience.  So they literally put pigs on random islands as full blown tourist traps to take money from naive tourists who want a swimming with pig picture for Instagram, but don't really know they aren't seeing the real thing.