What are those?

This snail in my 4l or about 1galon glass has crawled above the surface. They do that sometimes.
But in the small amount of water stuck to the snail there are these small white things frantically moving about.
Sometimes it seems like they uncoil and then they briefly look worm-like.
For additional scale the snail is 7mm or about half an inch so the swimming things must be around 0.1mm