Octopus

Octopuses are notoriously good at hide-and-go-seek. Their camouflage allows them to change color and texture to hide from any impending danger. You may never know if an octopus is lurking in the depths.

Giant Japanese Spider Crab

It’s essentially a giant spider that lives in the ocean, who wouldn’t be afraid?! But all jokes aside, the giant Japanese spider crab is awesome. With a leg span able to reach 15 feet, these crabs are some of the world’s largest crustaceans.

Divided Flatworm

This invertebrate makes our list due to its coloring. Divided flatworms can grow over 2 inches in length! They may be small but the award for greatest Halloween spirit goes to this divided flatworm.

Sawfish

If you are afraid of sharp objects, stay away from the sawfish and its protruding weaponry.  Their saw helps them detect electric pulses produced by their prey. These scary looking rays mainly eat fish and crustaceans – watch out giant Japanese spider crab!

Sarcastic Fringehead Blenny

The bulbous, outward-facing eyes of the sarcastic fringehead blenny make it look like a something out of a scary movie. These fascinating-looking fish are known to participate in some very interesting behavior when defending neighboring territories – I wouldn’t trick-or-treat near their house.