Best not to worry, but the odds are likely with you if you:
Are not out in the open (the middle of the river) (my situation the 1st time I was struck)
Are not in the water (it is still a huge flowing conductor and your boat is still pretty thin, there are often still water electrical paths for any boater in the water)
Are not under that outcropping with flowing water going over you (my situation the 2nd time I was struck)
Are away from things likely to get hit and/or fall on you (trees).
Are kneeling, not lying down, legs together, feet together, arms in tight, making a low ball of your body connected to the ground.
Are not anywhere near me.
I call bullshit on not being hit down in a canyon, there are many reasons this could happen, saturated soils, rock layers with higher conductivity, I have seen lightling strike on the landscape many times where you would not expect it...downhill from the grounded tower, etc.
Many hits involve already disbursed current and just become good fireside stories. I have met many people that have been struck, 2 within a day of my 1st strike.
I now carry a instaportasphere in my pocket (kind of like a fire shelter), check it at instaportasphere.com.