Creature Decoy

The Creature Decoy is a deployable tool, crafted using the Fabricator. It acts as a distraction device to attract hostile creatures to it when deployed, giving the player the opportunity to escape whilst the creatures are distracted. It can be deployed by hand or from the Cyclops.

The Data Box containing the blueprint for the Creature Decoy can be found in Lifepod 4 and the Underwater Islands Wreck.

Uses
To deploy a Creature Decoy from the Cyclops, there must be a decoy stored inside the Decoy Loading Tube. The decoy can be deployed while piloting the Cyclops by pressing the decoy button located in the top right of the Cyclops' HUD. When a Creature Decoy is launched from the Cyclops, it is displayed as a yellow orb on the Cyclops' hostile creature display.

A Cyclops Decoy Tube Upgrade will increase the capacity of the Decoy Loading Tube, allowing multiple Creature Decoys to be loaded at once.

If after that, the fins are still there, Try looking in the spawn locations of the Ultra Glide Fins.