A smaller version of the Prawn Suit’s grappling hook for the diver to get around quicker.
Cool idea!!!
I think an outright copy of the prawn’s hook would probably break the balance of the game, but something that’s sort of the opposite of the air bladder could work.
I’m imagining a winch that can shoot the anchor a very short distance (just for convenience), and is intended partly as an emergency escape (like the air bladder) and partly as a navigation aid to prevent getting lost in tunnels (presuming it’s technically feasible to implement the cable winding around the environment geometry).