Science! For Parties- Backwards When Wet

I don’t know about you but we here at the Eclectic Eccentric are firm believers in the saying that “a party isn’t a party until it there’s an optical illusion involved”. What’s that? You’ve never heard of that saying. Well, that’s odd because it is totally a thing. Anyway, where was I? Oh, that’s right optical illusions. Well in this edition of Science! For Parties, you’re going to learn how to make an arrow reverse course using nothing more than a glass of water.
For this trick, you’ll need...