I have been in something like 35 Kts, I missed some thunder heads that were hiding behind a tall dyke.
We had room to run so we first tried to match the wave speed by steering a broad course (surfing!) to and fro. Needless to say the room ran out on us and the scheduled ferry was out there... somewhere. We couldn't see anything (actually it must have been about 60 yards (20m)for all the flying spray and rain.
I didn't want to ditch because of the damn ferry. No way he would have seen us if we were upside down. I headed up as much as possible and we managed to hang on there somehow as the lightning struck left and right. Plan "B" by this time was to ditch on the slowly shelving lee shore of an island to get out of the way of the ferry, which then passed by us like a wall of grey iron, cutting off part of our already small circle of visiblity. The worst was over quicly after that and we had a blast getting back to the rental place. They were really happy to see us (and their boat) in one piece, (well almost, we tore out a trapeze bungee and a footstrap) it obviously wasn't the outcome they had been expecting...