Why is it faster to run on a wet beach than on a dry beach?

Because the sand on the dry loose beach is loose, it will bury your feet, and it takes time and effort to run step by step. On the wet beach, the sand grains are adsorbed by water and hardened, so it is not easy to bury their feet, which saves time and effort to run. So running on the wet beach is much faster than running on the dry beach.