The Octopod's periscope breaks off during a storm and lands up on a beach, lost amongst other marine debris. The Octonauts clean up the beach whilst searching for the periscope but a resident colony of fiddler crabs mistake the GUP-D and its claw gestures for a hostile giant crab and attack. The GUP-D goes haywire with a fiddler crab at the controls and burrows under the beach causing a sink hole to appear which almost swallows them all up. In the end the crabs fill the hole in with the sand balls they regurgitate whilst feeding.