Minecraft wiki entry for Things_not_to_do, associated text: Creepers submerged in water cannot destroy blocks and structures by exploding, but the slowing effects of the water make it especially tricky to kill them effectively. Unless the player wants to make it explode to get rid of it quickly without affecting the terrain, the player should use a trident or bow instead of a melee weapon to kill a creeper submerged in water. Ideally, the trident should have Loyalty to allow the player to throw the trident without having to swim to retrieve it.