Aculeozzo

The Infected Blowfish is a strange, fish based creature that appears in Resident Evil: Revelations.

They can only be found during raid mode. They appear as large, bright orange puffer fish. They cannot perform any attacks, nor damage the player in any fashion. At most, they can flop around harmlessly on the floor.

They have extremely low health, but incredible defense - so much that it renders most weapon attacks to a minimal 2 damage.

During Raid Mode, they tend to appear in optional areas. Upon defeat they will reward the player with a Weapon Case, which has a high probability of containing a stronger weapon.

Since they are only found in Raid Mode, it is unknown as to what viral process created them, if they are even a canonical enemy, or if they are just simply created as a gameplay mechanic unique to Raid Mode.