The bug

Frost walker ice, created by using the Frost walker enchantment on water; only has an collision box for entities.

This creates the following bugs (may be incomplete):

• You can't use splash potions on the frost walker ice, they fall straight through it *.
• * Eggs, snowballs, arrows (any projectile) will also fall straight through the ice.
• You can mine through the frost walker ice.
• You cannot place blocks on the ice.