The Crab Monsters look like normal crabs, albeit with noticable anatomical deviations. They are orange and white. They have two claws and six legs. They have one spike at the top of their heads. They have only one eye just like Bixbite.
They only appear twice in the episode. First when Ronaldo is recreating the Gem Warship crashing, one pinches Ronaldo's hand. The second time is when the Crystal Gems are fighting Bixbite. It is unknown what happened to them after Bixbite was poofed (the functionality of Holo-Pearls and the Drill Parasites imply that they can likely remain active despite Bixbite being poofed).