I think some of them have probably tried to work with their local marina to find a place to dispose of the vessel. It's probably disposed of at a landfill through dismantling the different components that can be recycled.
There was a program in Ontario funded by the Ministry of the Environment that was looking at grinding up the fibreglass and turning it into cement. There are a lot of these opportunities in other parts of the world. That funding ceased to exist a few years ago, so that went away. There's an opportunity to go back there.
There aren't a lot of great solutions for disposing of them responsibly.