I found a couple that claim to be high speed but haven't found anything that approaches that video. That's got to be less than a tenth of a second spread out in that entire video.

Sea water (salt water) conducts electricity very well.
Fresh water does not. Hence, being on a cat in rain, not touching metal, you can stay not grounded to the sea.

However, if your trampoline is sprayed by sea water from wave wash, you are probably very unsafe.

A drysuit may help a lot.
The wet surface may act as a Faraday cage, maybe?

A friend of mine wearing a drysuit was struck by a lightning on the beach. He told me that he observed the flash travelling on the surface of the suit and felt the pressure, but was not injured. At least he claims he was not injured.

Would be nice if someone got the physicists who really know about lightning to come up with consensus recommendations for (dinghy) sailors.

Stein

The only beachcat I ever heard of being actually hit was Sue Walsh's at the Rudder Club in Jacksonville, FL, about 1970. Her Hobie 14 was hit on the river. She sailed in all shook up. Spectators went to look at the boat as the mast fell down- the bow bolt holding the split forestay had melted thru the fiberglass. No apparent damage to Sue.

See many scientific references at http://www.lightning.ece.ufl.edu/
The University of Florida Lightning Research Lab Prof. Martin Uman (also Dr. Ian McEwen now retired), have given lectures to sailors on this subject: Grounded sailboats get really badly damaged (pinholes and blowouts) unless there is a huge grounding plate attached thru the hull. PS: Do NOT run across Florida waters in a speeding powerboat with many lightning rods sticking up (otherwise called carbon-fiber fish poles). Many deaths result yearly from this.

PPS: Carbon masts explode- near the top? I saw a new Viper that contacted a powerline in the 2008 Mug Race at Palatka parking lot. Exploded a softball sized hole at point of contact.

I have had lightning strike the water next to me twice. Once on a prindle 19, that one shocked me as I had an aluminum tiller, since switched to fiberglass. The other was on the way to the bahamas, there were 4 of us keel boats traveling together. Lightning hit the water between us all, but not any of the boats. That was a real head scratcher. What made it even more troubling, was we were sailing Hobie 33's. Because our fuel tanks are so small we have about 6 cans of gasoline tied along the rail so we had enough gas to make the trip. We thought that would have made a nice picture. Later that week during the Abaco regatta a boat got hit sailing during a race. Also recently had our cat hit on the beach while is was on the beach wheels. Our conclusion was it would have had less damage had it been grounded better.
I think real answer is we have no clue. Best to avoid lightning storms if you can. So you still raise your hand to answer this question.

I don't think it is as much of an issue that "we don't have a clue" but rather that lightening is unpredictable. Different atmospheric conditions can see the lightening behave in very different ways.