You hear of lightning strikes to sailboat masts from time to time, but I've never experienced one. The wire stays are thought to provide a pathway to conduct the electricity down into the water. Some people trail wire from the turnbuckles into the water during a storm to assist that process. Also, lighting protection systems are available commercially.

Most of the boats these days are fiberglass, a very poor conductor, so if you stay in your rain gear (usually rubberized fabric or PVC) and don't touch anything metal on the boat, you aren't too likely to get fried. Or so the theory goes.

IMHO proper boating safety during lightning is, as CANOEDOGS said, to get the heck off the water.

Frank2135