I think it would be cool to increase the “threat level” of creatures you encounter in-game. Most creatures deal chip damage to you. Also, there could be variations to creature attacks.
Bulletheads
Personally, PDAs related to bulletheads are positively disturbing, but they are merely a nuisance in reality. It’s also not immediately clear how to deal with them, since they do tend to swim quite fast & follow you for quite a bit. Twin sitarays probably share similar issues.
Needlers
The needler mangoes could be “upgraded” to feel more like a threat, because currently, I treat enamel collection as another day trip to the supermarket. I can see how this may be a problem for resource collection, though, so it’s possible to add some deposits slightly out of reach of these buffed creatures. Melee attacks as some have pointed out, maybe more damaging needles.
Great Jaw
Finally, the great jaw is also kind of weak. Apart from the damage, perhaps a couple more triggers could be added for the scare or danger factor. Maybe the eyes could already start to open as soon as you enter the chomp zone, or maybe the shell could close faster.