New Game Design/Gameplay needed for dealing with Enemies in future games

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I'd like an enemy that you can't HEAR. The hammerhead shark would have been a great chance to make such an enemy, or any kind of marine life. You have to spot it to be able to avoid it. Sure: The angler fish is such an enemy, but you can spot it a mile away. The reason why people feared the creeper in Minecraft, was because you could barely hear it.

That's why I would like to see an enemy that also uses the sneak mechanic not just the player, I see great potential in that idea but it would a hard task to program.