Hahahaha wat!? So hold on a second. Saki was turned invisible, probably because she didn’t want to be seen (or heard) by the islanders, and if she put clothes on, you’ll only see the clothes. So she chose to stay naked… THROUGH THE WHOLE EPISODE! Hahahaha oh god I in my pants~
Not only that, but she walked outside touring the island with her friends… That’s brave of her. Not knowing when her invisibility would wear off and she still went outside with no clothes on! A tour of the town naked! Seriously, Saki, what are you doing to me! Just remembering and I get a nosebleed.
One last thing… there are two wish granting rocks!? What the hell? Maybe the girls are the ones with the wish granting power? Dunno what…
Open Your Mind 
Hey, it makes more sense than seeing disembodied, floating clothes walking around the island!
That’s right.
But she was very quick on going out naked, no hesitation! lol