On the scuttling from an environmental impact view....
Scuttle the boat and it will sit at the bottom and nothing on it will ever be recycled simply because of the expense. It will instead sit there slowly breaking down slowly infusing it's components into the sea.
If instead it drifts onto shore, anything that is on the boat when it does can be cleaned up and recycled easier.
So scuttling is the ultimate 'out of sight out of mind' solution, it does NOTHING for the environment.
As for recycling the hull, I once had a shed that the roof was an old 14ft fiberglass dinghy, was the ultimate in maintenance free roofs, painted once every few years simply to make it look good.
When I moved in, the boat was in the woods behind the garage with the floors and all other wood rotted out, way too much effort and expense to make it a boat again, but was a great roof