Using tanks and ships to make reefs and amuse divers seems to be a popular activity. YouTube is full of videos about the organised sinking of ships and dumping of tanks.
The US has recycled at least one aircraft carrier in this way.

Maybe that is the reason for imposing import taxes on Chinese and European steel .... The steel has become so cheap that it can be dumped in the ocean instead of recycled.
Hmmmmm.......

/ Robin