For those that don't know who this monster is, this is Topo. Aquaman's pet Octopus.
His pet CTHULU-sized Octopus. Superman has a dog that can fly, Batman gets a Great Dane, Wonder Woman (in the silver age) has a giant Kangaroo, Klarion has a magical cat...and Aquaman has a SEA BEAST!
All arguments that say Aquaman is lame is invalid. Sure in the new 52 he has a dog, but he still has Topo.