Just looking like crap and nothing more than a pipe rising from the sea does not make them abandoned. There are thousands of caisson type platforms out there in shallow waters that are nothing other than a postage stamp atop a pipe. You can tie to them, but can be damaged and can be held responsible for damages.
The law states that any well is to be plugged and abandoned and well casing is to be cut off below the mudline, along with the surface structure removed after a predetermined period of no production. In practice, it's more difficult, especially when you consider the number of orphan wells that exist. These are wells where the path of ownership
is cloudy, or there have been several bankruptcies....etc.