Every summer we can count on at least one good lightning thread.
According to the Lightning Safety Institute or some such body, the only safe places to be in lightning storms are a "substantial" structure or a completely enclosed vehicle. Other than that, you roll the dice, because lightning is completely impetuous and unpredictable. There are no rules. It can strike anywhere.
If you live in the mid Atlantic region, and you pursue paddling in summer, especially if you take overnight and longer trips, you are going to get stuck in a lightning storm sooner or later, either while you are on the water or camped. Short of finding a substantial structure or completely enclosed vehicle, you are going to be at risk, and it doesn't matter much if you get out of your boat and kneel on your pfd, keep paddling, under trees, not under trees; you are at risk.
I take comfort from the stuff I see sticking out of the water. There are duck blinds, pilings, osprey nests, navigational markers and the occaisional tree. Such objects are usually considerably taller than I am when I am paddling, and if lightning is such a huge risk, why do we still see these things on the water? Why are they not charred by lightning strikes--these things are out there for every storm for years on end? OTOH, we don't see those objects that got hit. They are not there anymore. But, if being 3 feet tall on open water automatically drew lightning, these objects sticking out of the water would not be sticking out of the water.
I do not disparage any of the advice given by other posters, but I maintain you are just as safe continuing your trip when lightning starts, repeating this mantra: small target, big water. It doesn't really help, lightning still scares me pooh-less.
I was camped on a river bank on the Potomac the morning of July 3. A booming T-storm rolled through from about 4-5 a.m. We survived. About 7:30 a.m., I'm sitting there enjoying some coffee and oatmeal, watching the mist roll over the river. There was no wind to speak off. Suddenly, there was a cracking, crashing sound as a large tree came falling out of the forest about 50' away, slamming down onto the riverside rocks. That's the second time I've been camped on the Potomac when a tree randomly crashed down on an otherwise peaceful morning. A fellow was killed on the C&O towpath the same day. He was biking and a tree fell on him. I'm beginning to think all this emphasis on lightning is misplaced.