Minecraft wiki entry for Defense, associated text: Slimes may spawn above ground during the day. Unfortunately, drowning traps are rather hard to make for slimes, because of the fact that they swim in water instead of sink. However, slimes can be easily defeated using bow and arrow. Due to their melee only attack, they can also be defeated by sword easily. Tiny slimes will not hurt you, though they will push you around. TNT is also very effective against slimes, though it's also quite expensive.