A snow globe is a sealed jar of water with something pretty inside. What separates one that looks magical from one that looks like a jar of cloudy water is two decisions: what you glue inside it, and whether you add glycerin.
Sarah from She's Crafty and She Knows It builds two here. The first one failed, and she leaves that in the video, which is more useful than a tutorial where everything works.
Glycerin is the whole trick
Plain water lets glitter drop straight to the bottom in about two seconds. Vegetable glycerin thickens the water just enough that the glitter drifts and swirls the way snow does. Six drops is the number for a globe this size.
Do not substitute. Baby oil, mineral oil and dish soap all get suggested online and none of them behave the same way. Glycerin is cheap, it is sold in the baking aisle or online, and one bottle will outlast every globe you ever make.
What went wrong the first time
The first globe used Model Magic to build a little snowy mound for two small owl figurines to sit on. It looked perfect on day one. By day three the water had gone slightly cloudy, and by day five it was murky enough that you could barely see the owls.
Air-dry clay breaks down in water. Sealing it with spray polyurethane did not save it, and may have made it worse by putting more into the water. So: nothing porous goes inside a snow globe. No air-dry clay, no polymer clay you have not tested, no paper, no wood, no fabric.
Pick a bigger figurine instead
The fix is not a better sealant, it is a taller figurine. Choose one that fills the globe on its own and you do not need a mound underneath it at all. The second globe used a single resin fairy, and weeks later the water was still perfectly clear.
Resin and solid plastic figurines are the safe picks. Cake toppers, small toys and railway-model scenery all work.
Give the glue a full day
Super glue on plastic is slow. It bonds skin instantly and then takes its time on the two surfaces you actually care about. Glue the figurine down, run a second bead around where it meets the base, and leave it 24 hours before it goes anywhere near water. A figurine that comes loose inside a sealed globe cannot be fixed.