Broken fin: Tie one of the leg straps of your harness to the back footstraps (chicken strap is best if you’re on a formula board) and let it dangle in the water behind the board. The drag of the harness acts as a temporary rudder, giving your board some direction and weather helm so you can sail it (albeit, quite slowly and without sheeting too hard) back to the beach and save your skin. This solution works best on smaller slalom boards and wave boards.
A few years later, again in Europe I broke my first ever mast (better I don’t say how many I’ve broken since then!) whilst out sailing on a large lake in Holland. It’s an awful experience, a loud crack and being thrown face first in to the water wondering whether you’ve been struck by lightning or a boat! Upon returning to the surface you’ll find your sail crumbled and distorted, sometimes with a huge tear in your luff pocket and if you were in my situation, a good 1km swim back to the beach!