Novel execution method

So I was watching the gif where a shark attacks an observation cage and gets inside, what if instead of getting in, it severed the cable and the cage dropped to the bottom of the ocean with the divers inside?Think of it as an execution method,you get locked in a observation cage with plenty of oxygen tanks around you so you wont drown due the lack of air. Then you get towed to the Marianas trench/some deep spot, and then the cable gets cut and youll start falling to the bottom of the sea, as everything gets colder and darker, how far would you go before pressure gets you? Or would you simply stop breathing air so you can pass out asap? Terryfing