My moment returns...
An antarctic scale worm Pokemon, possibly a steel/bug or ice/bug type. These things may as well already be Pokemon. They xenomorph-style shoot out this fanged proboscis in order to catch prey. Also, unlike most worms, these things are active hunters, meaning they will actively swim around and seek out food. The reason I offer the steel type, though, is because they have these pretty gold bristles lining their body. Just look these things up. They're absolute beasts.
I'm also adding a hint of bobbit worm and almost anglerfish-type vibes to the Pokemon's behavior. Just for added flavor.
Onto the Pokemon itself. These Pokemon have wide, soft bodies lined with pyrite spines. They use the movement and shine of these spines to draw in prey, before shooting out a toothy steel maw to snap up the unsuspecting wishiwashi or magicarp. Its grip is powerful enough to puncture metal and snap bone. Divers are recommended to avoid this Pokemon at all costs for its rather aggressive nature, though a few brave souls still choose to call these creatures partners, as all it takes is a sufficient meal to gain their trust.
Finally, name concepts: Drawam, Prystle, Grawpul