How can a snail advance so fast?
A snail doesn't have legs to run with. The bottom of his bodice is one big “foot”.
With his body he makes wavy movements, so the snail moves forward. The snail can move that forward at about 50 meters per hour. The smoother the surface, the easier it can move forward. Therefore, the snail secretes its mucus. So that it glides nicer over the surface. Of course, you can see that slime trail very clearly!