This is an NPC, or a non-player character.
The Ghost Shark is a type of ghost which was introduced on Halloween Week 2016.
During a Halloween Week, all regular Ghosts are replaced with Ghost Sharks, which kill players upon contact, but appear faintly to them, even if they aren't equipping a Spectral Goggles or Synthetic Oculum.
When killed, one of the following messages will appear from the player:
- CHOMP CHOMP
- GHOST SHARK ATTACK!
- GHOOOOST SHAAAARRRKK!!!