I once did a calculation of lightning strike probability for a lone
sailboat and unfortunately I lost it and am too lazy to repeat it. It
was based on the number of lightning strikes per surface area per year
in a given area times the cone of protection area produced by a mast
of certain height and taking into account how much you sailed. What I
got was a number expressing the probability of a lone sailboat under a
storm being hit by lightning, it was surprisingly high. I had a long
argument about this in a sailing NG but eventually I found the
insurance company stats and they were remarkably close to my number.
What I do remember is that your probability of being struck went up
with the SQUARE of mast height so a mast or tuna tower twice as high
as another quadrupled your probability of being struck.
This number said nothing about the probability of a sailboat with
others being in a marina being struck.
So, after this calculation, I am very careful about sailing in
thunderstormy weather.