We did a month of boat touring around Italy/ex-Yugoslavia last year and mobile coverage in anchorages is very much hit or miss. Generally ok for browsing but video calls worked ok may be 30% time. Essentially you can't count that you can take work call and have decent experience. Huge inconvenience. I had a few "can't miss" calls and essentially I had to get to city 1-2 hours beforehand and then look for hotel/coffeeshop with decent wifi .