Endermites spawned in water by an Enderman act crazy and can't be hit.

I was in creative mode, I wanted to kill an enderman for fun.He spawned an endermite in water and I tried to kill it...But this endermite was acting weird and I wasn't able to kill it.
I even tried to remove the water but he still acts crazy and he is kinda invincible.
I tried TNT, fire,lava,arrows, lots of punches,sword...Nothing, he is still here.