More Water Monsters

Humboldt squid (mollusks) are skilled hunters found off the coast of California. Fisherman who work around these beasts have coined the term "Diablos Rojos", or "Red Devils" due to their  sharp ringed suckers, strong beaks, and speed (up to 25mph). Despite having relatively large brains, their rapid development (think macroscopic to 6 feet long within a year and a half) leads to extremely aggressive behavior, and they have been known to injure fisherman and divers
This video from KQED is long, but pretty alarming, since it explains these squids are basically taking over the oceans on the West coast.