https://luxurylaunches.com/transport/the-abandoned-alfa-nero-superyacht-is-burning-2000-of-diesel-everyday-to-run-its-air-conditioning-just-so-that-mold-and-sea-water-do-not-ruin-its-opulent-interiors-and-expensive-paintings.php
https://luxurylaunches.com/transport/the-abandoned-alfa-nero-superyacht-is-burning-2000-of-diesel-everyday-to-run-its-air-conditioning-just-so-that-mold-and-sea-water-do-not-ruin-its-opulent-interiors-and-expensive-paintings.php
Go for a swim with a hand drill.
The ecological effect of sinking this would be offset by the longterm reduction in pollution it creates anyway.
Sinking of the Rainbow Warrior except good and justified.
It's probably a steel hull. The easiest way to sink it would probably be to break some through-hull connections below the waterline. Not much you can do from outside other than perhaps plugging the bilge pump's output.
Or you could wait till a big storm and cut the docklines.