Permanent markers, like Sharpie makes, rely on inks with a strong adhesive to stick to almost any surface you write on. But dry erase markers use inks with a minimal adhesive, making notes and drawings that can be easily wiped away afterwards.
The ink in dry erase markers is also insoluble. That means it can’t be dissolved in a liquid, and more importantly, it means it’s less dense than water. When you pour water onto a dry erase word science on a smooth surface (Plate for the Dollar store), a strong buoyancy force overcomes the stickiness of the ink, pulling the word science off the surface and causing it to float on the water.