My kids loved to do this after all those rains. The yard was full of snails – small, big, and even bigger.
Take a chalk and draw a circle. Put the snails in the centre, in a smaller circle, and place some green leaves around the circle for a “bait”. The snail to reach first the bigger circle is pronounced the winner.
You may put tags on them, or just mark them with chalk, to be sure which is which.
Interesting fact – the shell may tell which snail is older. Each whorl or spiral means a new increase. The snail grows inside the shell, so the shell grows at the end and thus new whorls are formed.