Lightning ?

seawater is a good conductor. Therefore with the boat upright you have a long pointed mast attached to an efficient earth. If you capsize the boat you no longer have a conductor pointing skywards. There are two risks from electricity the first is that current flows through your body. If you are swimming in a good conductor your body is unlikely to be the path of least resistance to Earth is not through you. The second is if you are close to the point of energy discharge where you might suffer burns from the flash or be showered with debris if something like a mast explodes.

While I don't know what the impact on fish would be I would only expect those very close to the point of the strike and near the surface to be affected.

how does a carbon mast with metal wings sound, get exploding red hot carbon splinters and your standing on a highly conductive bar. Perfect.

omg that sounds horrible lol ,  well yeh being drtuk by lighting whilst sailnig would scare the  outta me

Hmm I'm not sure if hydro would go in such extremes to be in the Picture of the Week topic!

oh ym that would give u a little buzz if u were hit by that bolt of lighting probobly would be a horrible but interesting thing to watch just as long as it wasnt happening to me