Europe went this way in what regard insurance decades ago. The first and sometimes the only thing they asked in a Marina was insurance papers. I was very surprised that in US where law suits are so common about anything that Marina owners would accept it any other way.
Now some countries are starting to ask for a special insurance that covers pollution and some are making mandatory for yachts in some areas to have holding tanks. Some even made illegal the discharge of holding tanks in their territorial waters meaning that they want to control were you discharge them and that means on a Marina, having to pay for the marina and the job